Currently playing Galactic Civilizations 2. Bought it on GOG back in 2019, finally got around to playing recently. It's a good game, different enough from Master of Orion 2/Sword of the Stars/Endless Space to be interesting. Also has campaigns, very unusual for 4X games. It's definitely an old game, as widescreen support is iffy (some things are stretched, like the videos), and it doesn't scale well to higher resolutions; 1408x792 was the best compromise I could come up with. There are font issues running in Wine, but I managed to (mostly) fix them, otherwise it would be kind of annoying to play.

Star Wars: Dark Forces
I don't play a lot of FPS games (I'm very bad at them), but once in a while I try one of the classics. And normally I terribly fail and give up after a while. But this one was very good in my eyes. I liked the setting , the story, the weapons and the level design. And also it wasn't that hard. So it caught my interest till the very end and is one of the few FPSs that I really enjoyed and actually completed.

Conquests of the Long Bow: The Legend of Robin Hood
I've played this some years ago for the first time and I thought it was amazing. Good and mostly logical puzzles, interesting story and it also looked pretty good for the time it came out. One of my favourite Sierra adventures.

Fallout 3
I'm playing it for the first time at the moment and I really like it. In fact I enjoy it more than the first two games which I played shortly after they came out.

* Max Payne
* Drakan: Order of the Flame
* Doom (granted, I knew it from the 90s, but had never played it much myself before playing through it a few years ago and thinking it still holds up)
* Quake (although I only like it in the recently released Enhanced version, because the old DOSBox version did not run smoothly for me)

Trails in the Sky (Originally released in 2004)

The biggest names are probably Baldur's Gate 1 and 2, Planescape Torment and the original Deus Ex that I played very recently. BG2 is my favourite RPG now. There are so many good games from the past that I am yet to play that I can barely look into anything new. Currently trying to play all the classic big names in the RPG genre. Dragon Age is next! Only problem is these games take so many hours...

Did you play Neverwinter Nights? That might be worth checking out since Bioware made that before Dragon Age but after Baldur's Gate.

Indeed, 5+ years was more of a rule than an exception for me just about all along, and after a while that began stretching towards 10 years, but 15 is pushing it, and I actually went through my list of games played and just came up with those few that I did play 15+ years after release and could still recommend.
But I guess that's just the point, to have a restrictive condition, not just list older games you fondly remember.

NWN is on top of my most played games with 300+ hours and this is just the single player campaign which I have never played before so I decided to give it a try finally. With the multi I have had a lot of fun nearly 20 years ago such good memories! It seems I will play them in chronological order then if NWN is between the two! ^^

Interesting topic thread. I saw it mentioned that the prevailing theme of someone who would have played games that fall into this criteria would be young people who ventured into the way back machine to see something from long ago, perhaps before they were born. But I think it would also be pretty common to have a scenario like mine where I played a lot of old games when they first came out, circa early 80s and onward, who missed some of those old classics, and only later down the road in life came back to PC gaming. All that said, here's a few I've enjoyed since coming back to gaming later in life:

Lands of Lore I
Eschalon: Book I

and my best recommendation Divine Divinity

Yeah. I just wonder if I'd had any reservations about e.g. Serious Sam or Starcraft, if I played them for the first time today?

I don't have any issues replaying them today and can easily forgive any jankiness they might have... but I wonder if that would hold true if I played them now for the first time? (I bought and played Starcraft not until Brood War expansion was also released so it was maybe a couple of years old by that time (it might be I even bought an used or discounted copy of those games), and I think Serious Sam games were also a few years old when I played them the first time).

With some old games that I played back in the day, I don't really forgive their shortcomings today. For instance, today I feel the controls of Ultima Underworld 1-2 and the original System Shock are atrocious and I can easily see they would put off people (including me) today. Fortunately the controls were fixed in System Shock by introducing proper mouselook and WASD-controls, so that is the version I propose people play if they want to experience the "original" System Shock. The WASD+mouse controls just make it so much more playable.

Still, I fondly remember those games, what kind of feelings they ignited in me when playing them for the first time and discovering the world/story within. I've never felt so lonely and freaked out in a game as in the start of Ultima Underworld, being locked into a dark dungeon with nothing on you; then discovering a torch and a bit of food near you which gave you some comfort. Then bit by bit discovering the living world and ecosystem that existed in that dungeon that I at first thought was just empty or filled only with mindless monsters...

The same for Doom and Duke3D games (and games with a similar 2,5D engines). I just can't get over with the limitations of those engines today, they just feel so fake, even if back in the day I didn't mind them and spent countless hours on those games and their mods.

If you want the full story (and haven't played it yet), maybe even playing the first "Blood Omen: Legacy of Kain" game before Soul Reaver 1-2 might make sense. They have partly the same characters within them, and in a way the story continues with each game, albeit I feel one can easily jump into the first SR1 (without knowing the story from the earlier game and that you actually played the SR1 antagonist in the first Legacy of Kain game; SR1 still makes some story and character references to what happened in the first game).

All the other games in the series are available in GOG, except for SR1 which was removed at some point, possibly due to the incoming remake:

Blood Omen: Legacy of Kain
Legacy of Kain: Soul Reaver (now missing on GOG; I have the GOG version though)
Legacy of Kain: Soul Reaver 2
Legacy of Kain: Blood Omen 2
Legacy of Kain: Defiance

I have recently finished Blood Omen and Soul Reaver, and are now maybe 80% finished with Soul Reaver 2.

One thing I don't like about these games is the console-like save game system. Usually it means save points, in the first Soul Reaver it was even more complicated (something like that you can "save" the game anywhere you want, but when you reload the game, you always start from the beginning and use portals to get where you saved; the state of the game world is saved though so you don't have to deal with the same puzzles and bosses you have already finished anymore).

For instance in Soul Reaver 2, I think at one point I played like 2½ hours before finding the next save point so that I could finish playing for the day and hit the sack... Usually it is not that bad (sometimes you find a new save point 15 minutes after the earlier one), but damn I sometimes miss the PC-like "save anywhere" savegame system...

There have been many, but I just played through System Shock 2 and I loved it. I was aware of the game when it was released since I loved Thief and Looking Glass Studios, but I never managed to play it before. Over the years I have had a few false starts, but this time I finally sat down and completed it. Now, being that it's a late 90's shooter, it has some shoddy design here and there. I really wish they'd either gone all-in on the resurrection mechanic, or the saving mechanic. As it stands, I see little reason not to just use saves constantly and just ignore the resurrection completely. The game also has a lot of backtracking that feels a bit too much like padding, and the late game feels a bit rushed and linear.

But none of that matters, since all the strengths of the game far outshine any deficiencies. The atmosphere is just spot on, with great visual (for the 90's) and sound design. Exploration is fun and oppressive and the game does very little hand holding. At times it can be a bit too opaque, but for me that was acceptable and just added to immersion. Good writing certainly helped. It was a wonderful experience and not as difficult as I feared it would be. Great game.

To be honest, as long as an FPS has "mouselook" and rebindable keys, games like Serious Sam FE / SE are still very playable even 20 years later simply because hardly anything beyond graphics has changed much in 20 years (and some stuff that has, eg, checkpoints vs quick save is more due to consolization than 'evolution'). The gap between System Shock 1 (1994) and System Shock 2 (1999) is 1000x greater (in terms of standardised FPS controls / clunky "early FPS learning experience" UI that takes up 50% of the screen) than the gap between SS2 (1999) vs many 2019 games. Serious Sam's are very much "arena shooters" but if you like that 'Fast & Fun' style of play, you'll probably enjoy them. The only technical issue I found (VSync / MSAA not working on old DirectX vs W10-11) was solved by switching to OpenGL (native to the game).

Lots of source-port options though:-

Doom Engine - https://zdoom.org/downloads
Quake 1 - https://github.com/Novum/vkQuake
Quake 2 - https://quake.fandom.com/wiki/VkQuake2
Build Engine - https://github.com/ZDoom/Raze

Looking back, I don't really feel that the limitations were fake. If anything, things like limited verticality (ie, no rooms placed directly above each other in Doom Engine) spawned off some massively creative level design techniques (atriums, etc) that went a long way in hiding it. It was probably the right balance between limitations vs hardware requirements for the time that was necessary to get Doom and it's DOS/4GW extender to load (with no small amount of CONFIG.SYS and AUTOEXEC.BAT tweaking) in common 4MB RAM for the day. As a teenager, I definitely wouldn't have appreciated Doom needing 8MB RAM back in 1994... ;-)

As for the subject, I think Planescape Torment is one I played for the first time in the mid 2010's and going into it with no "nostalgia hook", the hype is justified. Far too many others to list from 90's FPS's to quirky shareware. The oldest examples I can find personally is finishing Colossal Cave Adventure (the original 1976) and Zork (1977) both in 2023. Even 50 year old games, quite honestly how well you do depends a lot on what frame of mind / mood you go in with (curiosity vs boredom, etc).

Yeah I tried a 3D engine replacement (could have been ZDoom or something similar) like 10-15 years ago for Doom, and it was pretty great, making the game much more modern so to speak. But still, if I'd rate the original game engine...

I don't think Quake really needed an engine replacement, it was fully 3D to begin with. Doom and Duke3D were not.

Back in the day it was great of course, there wasn't really anything better and it was really a sight to behold. Still, I recall how odd it felt that in some user-made map there was a very high tower, and I could just drop from the top of it like it was nothing, things like that broke the immersion somewhat already back then.

Then of course there was Ultima Underworld which appeared before Doom, yet seemed to have a more "3D-like" engine. Doom was much flashier though and with a full-screen view.