Looking for a particular kind of game ...

[frogbeastegg]

Nice to see someone else who played Startopia. I adored it back when it was new; I upgraded my video card so I could get it to run smoothly and on full settings.

Tropico is on my list of games to pick up now that it's been re-released as a cheap downloadable 2 pack. I couldn't cope with playing it now; I have an 80 hour JRPG and the sprawling Sword of the Stars on the go. One more large game and I'll drown.

[Sheogorath]

Bah, you had to go and play it beforehand :P

AH, well...I might suggest the old Dungeon Keeper games? One and two are both good, although you might have trouble getting them to work on a modern computer.
A small-map DK2 game lasts only around 10 minutes or so. The campaign is longer, but eh.

[TinCow]

Evil Genius - A building sim, ala Simcity or ThemePark, but where you play a 007 style evil villain and build a lair. It's a flawed game but very fun for a good while and it's also very amusing. $10 from GOG.

Painkiller - Pure mindless FPS fun in the Serious Sam style. Makes no pretensions at storyline and such. Just boatloads of enemies, interesting level design, and fun weapons. $10 from GOG with expansion pack included.

[FesterShinetop]

How about Mirror's Edge? It looks nice, has good production values, not too long and you can get it pretty cheap nowadays.