I can only make recommendations based on what I played...
Here's some that I highly recommend:
Fallout, New Vegas:
Excellent 1st/3rd shooter RPG where actual choices really make a difference (unlike fable) in how the game unfolds. Tons of endings and lots of replayability even without the expansions, though the expansions are certainly worth playing too. My fav expansions were lonesome road and old world blues. I have about 190 hours logged in this game.
Free to play MMO through Steam, excellent for creating custom character pics for Supers PBP Games. It's not terribly remarkable, but it's solid and done very well and the clincher is that it's completely free. There is an item mall, and I've dropped maybe 15 bucks in it since I started playing and I have about 190 logged hours.
Best PVP action MMO for fantasy. I had to stop playing because of game imbalances on the servers, but while it was balanced it was the best PVP ever... zoned castle sieges on T4 were amazing! Nothing like commanding an army of 100+ epic level characters against 100+ epic level characters over a huge zone with several keeps... it was intense
Gotta love portal games.
Blood Omen/Soul Reaver Series:
By far my favorite video game series. The early games are really dated by this point but if you're in the mood for retro, do it up. These games were among the first where you get to play a really nasty villain, and you do get the sense that you are actually evil and not in the cheesy comic book sense. You really should play the whole series in order because it won't make sense otherwise.
Mass Effect Series:
While Shorter in content than Fallout NV, this is also an excellent shooter RPG. Where it lacks in Expanse it makes up for in being plot focussed and having a tactical combat system more evolved than quake.
Batman, Arkham Asylum:
Amazing stealth/combat engine that excells at both without making the other obsolete. Fun game and am very much looking forward to Arkham City on the PC next month. Only complaint was that the game was too short and I could have played this game for another 3 years and been happy but that's more of a compliment than a complaint.
Ultimate Strategy Game. Never seen anything done as well. I force myself not to play this game though because if you do, you start, then realize instantly 4 days have passed and you really need a shave and a shower. This game is so immersive you should plan ahead with lots of energy drinks, snack foods and and a clear schedule for at least 2 days.
World of Warcraft and EVE:
I hate recommending these two games because they are soul sucking and evil, but they are really good. I do not ever recommend anyone plays them, but it would be a lie to say they both aren't great games.
the new Deus Ex, I am looking forward to buying this when it goes on sale. Same with cities xl 2012
I would also note that there are several big name games I would advise against, but yeah... these are ones I would recommend.