I would list Blizzard, but they're getting extremely lazy with WoW, namely with their itemization and class balancing. All classes are essentially carbon copies of each other, and they only make a couple items per tier now and copy and paste different stats on them to pass them off as different items. That's just straight lazyness.

Bethesda makes solid games, and Bioware games are great too (even though they tend to look years behind the graphics curve). Oh and Valve for sure, these guys set the bar for post launch title support

Starsiege Tribes

Alizerothree

It's being remade into a browser game I think

http://en.wikipedia.org/wiki/PlayTribes

I love the whole forge thing in reach, but after recently going back to Halo 3 the gameplay just feels way too slow compared to CoD (or really any other FPS game). Dunno if reach is faster or not, but if it's as slow as Halo 3 is then I'll be playing black ops.

I don't know if regret is the right word, but I wouldn't have bought most of the arcade games I own right now. That's a lot of money wasted on those little games I never play

That's the same with pretty much everything you download off the xbox marketplace.

Edit: Oh, just RTS and not turn based, hmm... Ensemble I guess. The Age of Empires series is pretty great