Hmmm, Darksiders just came out for PC.
Overlord is a lot of fun and I hear Overlord 2 is even better (own both, haven't played the second one yet).
Mass Effect 1 and 2 are a lot of fun (IMO 1 was better, they "bro'd up" the second one).
Dragon Age: Origins and Dragon Age: Origins: Awakening (the expansion) are tons of fun, and the DLCs are fun, too. Hope they don't "bro up" Dragon Age 2. Consoles are not the appropriate platform for real cRPGs, they're only okay for jRPGs (which tend to suck anyway).
SINS of a Solar Empire is the tits as a 4X. Dawn of War is an excellent skirmish-level strategy, and Dawn of War II is a really fun pure tactical skirmish game. Note: the multiplayer on these three games blows that of Starcraft (I and II) and Warcraft (I, II and III) out of the water. OTOH, SINS doesn't have a campaign mode; and the DoW games have so-so campaigns, story wise.