Cybermage: Darklight Awakening - FPS, Sci-fi, Super person saves the world from an alien invasion gone wrong. Some overlap in publisher/developer with System Shock. (You're gonna need to figure out how to jump because its not listed on the in game key listing and I've forgotten what combination of keys it took to do it.) Pretty solid game after you get the hang of the "magic powers" system.

Heroes of Might and Magic. The earliest installments are abandonware ... or at least findable on abandonware sites. Solidly enjoyable for a bit before it gets monotonous but I just use that as the sign that its time to stop playing and go do something else.

Transformers: Devastation is ... fuck... its amazing. There's a few versions uploaded to the Clearance Bin section at Archive.org. Watch some YouTube videos to see what you're getting in to. Pick one of a handful of the Generation 1 Transformers and brawl your way through 3D levels that and pretty much "play" an episode of Transformers. Characters level up, there's some weapon crafting, some looter shooter mechanics, some hard to find pickups that unlock character/scene art (unlocked a picture that I had on a lunchbox when I was in elementary school that I'd totally forgotten about). If you ever wanted to fist fight Devastator with Bumble Bee or pile drive a Stuntacon with Grimlock, this game will not disappoint. I was really surprised how well this ran on my toaster of a computer.

Clive Barker's: Undying. FPS with some Lovecraftian Horror themes. A bit heavy on the jump scares but there's a few parts that I found genuinely creepy. Which they didn't give to the hero "jokes" to say, really gets in the way of the creepy horror vibe. There's some CD keys in the comments, one of them worked for me.

Space Crusade. Warhammer 40k turn based squad combat. All the way from 1993 to fulfill your "I rolled 4 dice + a reroll and all I got was five zeroes" needs.

Edit: AAaaaaannnndddd I just checked and it looks like Planescape: Torment is available on abandonware sites. Maybe I'll get around to trying to beat it.

Annnnd Space Rangers. Very hard game, very awesome. (I've only ever beaten it on the easiest difficulty with the easiest to start with race and easiest to start with class.) Ever play Master of Orion? Know how you get to build space armadas and go colonize the galaxy? Ever notice that there's "trader fleets" that you see numbers about sometimes but don't actually get to order around? Ever want to play as a single ship flying around doing commerce, bounty hunting, piracy in a galaxy where some Master of Orion stuff is happening all around you? Well, here is the game for you. You flit around the galaxy trying to make money while an alien invasion is slowly taking out systems one planet at a time, all the while all the NPC's in the galaxy are actively doing things (its kinda impressive really).