I'd recommend you try witcher 1 and 2 (make sure to try 2nd one if you don't like the first one much)
Dota 2 should be coming along within the next 6 months or so (it's in beta right now) (same as league but more professional feel to it as it's got harder mechanics)
Mass Effect series - great graphics, great story line, pretty decent gameplay
Dragon Age: Origins - very good "remake" of classic style squad RPG battling in typical Bioware style (deep companion conversations and such) great graphics and plot
Portal 1 & 2 - based on source engine, 1 was very good plot and puzzle game from what I hear. 2nd one recently released has added multiplayer which is loads of fun.
If you like free exploration fps games like farcry and crysis, give Stalker series a go (Stalker: shadow of chernobyl, clear skies, call of pripyat)
Metro2033 is a scary post apocalyptic shooter with tremendous graphics as well.
Civ 4 or 5 have nice gameplay, alternatives if you don't like turn base include Dawn of Discovery and Anno 2070.
Racing games Dirt 3 and GRID have had their amount of praise. I'm not recommending any NFS titles since I've lost all respect for them.
For multiplayer give Team Fortress 2 a try if you haven't yet (it's f2p on steam). Left 4 Dead 1 & 2 were said to be lots of coop fun, but I don't know how alive the server population is by now.
SW:TOR recently launched, and if you're a star wars fan, I think you will like it. Otherwise other highly anticipated titles are Diablo 3 and Guild Wars 2.
Well, that's about all I can think of and just about covers every genre out there.