Oasis, IMO, deserves a mention, at least the category of board game-like or abstract strategy. Oasis thought it was an interesting take on the 4X school. Unfortunately, I can’t think of another good abstract strategy game-- Darwinia or Defcon might count but I haven’t played them. I have played Republic: The Revolution, and while it was an interesting game, it was also badly flawed.
For builders, I guess I agree with the nomination of Zeus. Caesar 4 and Children of the Nile are good building games, but not must play. There’s a few modern builders I haven’t got around to yet, such as City Life. I was unimpressed by Sim City 4.
I’ll mention The Movies as a “should try” management game although The Sims clearly dominates the category. Another flawed game, though-- too easy by half in the early days and lacked late game achievements.
I’m not a big RTS buff but the best I’ve played from the last 10 years were Kohan II and Rise of Nations. I remember both getting quite good reviews-- Gamespot in particular seemed to think RON was a revelation-- but I suppose they failed to get a multiplayer following or something, because they’ve seemed to nearly disappear from memory. Both were good for single player and the short game. A decent AI can beat me so I don’t need a human opponent. I also find the campaigns in strategy games generally unappealing, at least the sort where you have a bunch of scenarios strung together.
To add another category, just so I can fit in a mention of Disciples 2, there’s turn-based fantasy themed strategy. IMO Disciples was worth playing just for the artwork, and was a solid game. The competitors that come to mind are Heroes of Might and Magic IV and V, and I’ve only played IV and found it good for a few plays, but it really depended on map design as the strategic AI was weak.
Thinking back over the RPGs that I’ve played, I enjoyed Planescape and Diablo II, but I prefer Dungeon Crawl Stone Soup and I’ve easily put the more time into and got more fun out of it than any other RPG. I don’t know when the original Linley’s Dungeon Crawl came out, but Stone Soup is a different version with a different dev team. I think Dwarf Fortress should get a mention as well. Hm, I wonder what the most recent version is like?