Stick with Guild Wars 2 until Elder Scrolls Online if you're fixing for some MMO, although DC Universe Online is very good for a F2P MMO. If you're running anything AMD, whether it be CPU or GPU you'd be better off avoiding Secret World like the plague, the game is horrible on AMD hardware, Metro 2033 runs at a considerably higher framerate with less stutter with all the DX11 bells and whistles than Secret World did on medium/low, horrible hardware biased game. Avoid WoW unless you feel like spending £120+ for the content, and then a monthly fee to even experience it.
As for single player games,
RPG = Gothic 3 Forsaken Gods/Skyrim
Shooter = Crysis 2/Battlefield 3
Fighting = Street Fighter IV Arcade Edition/SFxTK
Sandbox = Just Cause 2/S.T.A.L.K.E.R.: Call of Pripyat or Shadow of Chernobyl/Prototype 2
Racing = Project C.A.R.S/Shift Unleashed
Stealth = Hitman Absolution/Splinter Cell Double Agent/Dishonored