ToME 4/Tales of Maj'Eyal. That's been my big time pit for a good while now. Good roguelike that's mostly what you expect, though on a larger scale than most of it's type that you can buy (and indeed, it's actually 99.9% free and the copies you get on game sites are basically the Premium version). Sword of the Stars: The Pit has also been pretty good (though perhaps a bit odd to some... think DoomRL meets Dungeons of Dredmor).
When has Age of Wonders ever gotten old? The third is like today's HOMM to me. King's Bounty was also good until the last two titles... they kinda lazed around on the job I think. They're still all good fun to some degree though.
Tropico's pretty funny but 5 wasn't so hot. I'd say 1, 3, or 4 is where it's at. Honestly 3 is more sandboxy and has better humor, so I wouldn't strike it out to say 4 is a straight upgrade. It's even better if you're the type that goes to the presidential debate thread a lot.
Soldak Entertainment's entire catalog is great if you enjoy Diablo-style games and don't mind the plot suffering a bit. The entire world is random in Depths of Peril and Din's Curse, and all sorts of things happen in town while you're out killing things, like villagers fight and people get hungry. Drox Operative is basically this kind of game in a 2D Escape Velocity style space shooter. Also, the Torchlight games are basically a Diablo 1/2 mix in a different setting thanks to who's behind it.
Also, the Avadon series is pretty good if your into that turn-based RPG with movement like an SRPG. Story may get old by the third game and I can't say much for additions outside of UI buffs and one new class in 2, but it's still all good. All of Spiderweb's games are grand (though I prefer the older Avernum releases until the third remake comes out).
Oh, and if you like Descent-style shooters and don't mind Roguelite elements there's Sublevel Zero. Surprisingly it's really well done. Ziggurat is also pretty darn good "normal" FPS of this type, the rooms may get old after a while but the combat's where it's at for this one.
Age of Decadence could be better, but I like the world quite a lot. If the setting appeals to you take a gander.