chimeracreator said:
Startopia: A very solid management sim set on a space station with a variety of amusing alien races, a fair bit of humor and a whole lot of options. Also some combat. Unfortunately it didn't do well and the company went under.
Dungeon Keeper: A game made by Peter Molyneux before he lost his groove. A wonderfully different RTS where you control a dungeon full of monsters all of who go about their daily business in addition to the whole killing adventurers thing because let's face it, sometimes a dragon just needs to sleep and lord knows you better make sure you pay it on time. There was a sequel so obviously it did decently, but the series ended there.
Freelancer: A modern take on a space sim that works with a mouse, has a massive open world and has a pretty solid plot. Yes please.
All great games and definite must-play for any PC gamer. Startopia is going to be a pain to run on modern rigs though, so be sure to check some online guides.
I'll throw in Zeus: Master of Olympus, a fun city builder in the style of Caesar III (think that was quite popular in it's day) but with some simplified gameplay elements. Do give Caesar III a go while you're at it. It's hard, but very satisfying to get a good city going.
Mount & Blade, it's not pretty, it's not user-friendly, and half the time you have no idea what you're supposed to do. But by gods the combat is worth it!
Jagged Alliance 2, it takes a while to warm up to the game, especially because it has a rather steep learning curve, but once you get the hang of it, it's great
Mirror's Edge. I'm not sure why this game got so much bad press, I think it might have to do with clunky console controls, because I found the PC version to be very good. Just pretend the story isn't there.
And you know what? I'm going to throw Terraria in here too. Don't know if it's underrated, but I really liked it. It's kinda like Minecraft, with the gathering resources, large random map, building stuff with the resources you've gathered, crafting, and so on. But it also has a progression of sorts. There's a lot of stuff to work towards, like killing a boss, getting an NPC to join your little village or just getting tough enough to explore further. Also the multiplayer is super-fun. Doing all of the above with friends just makes things a whole lot better.
Oddworld: Abe's Oddysee and Exoddus. Puzzle platformers with some very unique gameplay and setting.