Master of Orion 1+2

As a disclaimer: I hadn't played Master of Orion in the past, so nostalgia isn't playing a factor here. I have played many of it's descendants though (Stellaris, GalCiv, Endless Space) and I can say with certainty that MOO2 remains the best 4X space game on the market. Overall, the game leans into its strongest mechanic: the tactical combat. There is a wealth of different weapon types, modifications to those weapons, and positions you can place those weapons on a ship. All of which matters significantly (especially at higher difficulties) and which will change depending on the race you're playing and who you're fighting. Not to mention it's just plain fun taking a ship you've built from scratch into a tactical battle with other ships to absolutely vaporize them - or to find out which loadouts didn't work. The tactical ship design is truly unsurpassed and unlike anything developed since then. This is to say nothing of everything else MOO2 brings to the table - a decently competent AI, excellent replayability, many races to choose from, a custom race designer, tons of research options, etc. Get this game if you're even remotely interested in space 4X, or even generally in 4X games - you won't be disappointed.

Old but gold strategy game in space. Each race feels unique and requires different strategies to succeed. Numerous tech paths provide substantially different progression depending on what you focus on. Ship design and combat has great depth and provides an enjoyable challenge. Sprite animation and interface holds up to this day. I personally prefer MOO2 for nostalgia reasons, but 1 is great as well.

Can mainly speak to MoO 2 as that's the one I plunged 100's of hours into. If you even have the most basic interest in 4X or Civ type games you'll abolutely love this one. All the concepts of a good 4X and Grand Strategy game are here, expanding into new planets, managing your colonies and fleets, researching technologies and advancing the tech tree, tense diplomacy with your rivals, allies and enemies. It's all executed so well here, and the satisfaction of seeing your fleet power grow, the buildings populate on each of your planets and filling in the map as you travel the stars and discover where your enemies are... its all just so well done. Each race has its strengths and weaknesses, and although there may be some races that are overall weaker than the others, it still lends to the games replayability as you try and maximize what each different race is effective at doing. Some are excellent at diplomacy while others are so hideous or disliked that they have little to no diplomacy options at all. It's easy to see where future sci-fi games of this genre found a lot of inspiration, and this one still holds up as a highly enjoyable example of why it remains a classic.

... Of any genre. Both of these games are landmark. I got at least 100 hours in Master of Orion 2 logged by GoG, and I played this game with my best friend back in high school when it came out. It never gets old. Even the old school graphics still look darn good! You get two games for six dollars that will each give you months, even years, of play time!

Master of Orion 2 for me is probably the best game of all time. If it were modernized in just a way to decouple the GUI from the resolution (but still keep the game as it is) I would still be playing it on my regular PC. The DOSbox version is a bit weird, and the original doesn't run on anything newer than WinXP. I keep an old netbook healthy just for this game.