I only had the chance to play Ripper as a demo and had completely forgotten about it. One of the few demos I played multiple times.

Plus for Christopher Walken!

Both Buck Rogers SSI games. Complete the Goldbox collection already GOG!

If this topic asked for 10 games, hell maybe even 5, Heavy Gear 1 would definitely be on my list. I don't know for sure but it wouldn't surprise me if I put 100+ hours into that game. I thought I was the only person who prefers Heavy Gear 1 over Heavy Gear 2 but I guess not,

Sentinel Worlds: Future Magic. Think "Bards Tale" but in space. Great game that isn't legally available anywhere AFAIK unless you can acquire some old floppies somewhere) but deserves to be played by more people. The sequel/follow-up/whatever would also be good.

For the other one I am going to say Command & Conquer: Renegade. FPS set in the C&C universe and all around great game IMO. (although given that I have spent the best part of 18 years pulling the game and its engine apart and making it better and am the lead programmer on the community patch and engine work, I may be a little biased :)

You can get C&C Renegade from Origin as part of the Ultimate Collection pack but having it DRM free here on GoG (and getting some exposure it wouldn't get on Origin) would be good for the game.

Honorable mention goes to Dune II (just because of how it basically created RTS as we know it)

I don't what it was about HG2, but I didn't care for it that much (acutally I don't remember much of it). Heavy Gear 1 though, I sunk in a lot of hours into that game as well. I still have the CDs for both of them, but last time I tried, I think I could only HG2 to work.

My main issue with Heavy Gear 2 is the controls. I have a very mild form of cerebral palsy that manly effects my legs but also effects my hands and fingers some. This makes using a mouse and keyboard control scheme for shooters, and mech sims much harder for me they using a pure keyboard control scheme, or a gamepad and I never figured out how to set Heavy Gear 2 to a keyboard scheme I was as comfortable with as the keyboard control setup I used in the first game.

Everything you said could be said of Centauri Alliance, except for a couple differences:
* The game *really* needs upgrades in terms of the interface as well as some major bug fixing.
* The game never got a DOS release, so the only way to play it on a modern PC is to emulate the Apple 2 or Commodore 64 version.
* Centauri Alliance never got a sequel.

No One Lives Forever 1+2 (if you want to count that as one)
Mass Effect Trilogy + DLC (also counting as one)