not many PC exclusive good shooters on fps tbh, those times are long gone unfortunately. Stalker and Crysis are good, but not great. 4/5
you may want to consider some RTS and MMO on PC as they seem to be the only type of real PC games left nowadays.
RTS: Company of Heroes and Starcraft II must have. both excellent 4.9/5 ( i don't believe in perfect games)
MMO: Age of Conan if you have the time to invest in MMO

4.5/5 problem was it was released with limited content after lvl 40 and got slated, but now with all the patches and added content it's very good/complete imo. definitely give the demo a try. obviously many others to choose from such as WOW, LOTRO, EVE
RPG: Titan Quest and The Witcher are ok 4/5
Sims: Arma, Rfactor and Flight Sim if you like those types of simulation games; they seem to be references in their respective categories. personally not my thing so won't grade them
all these games look good on PC and will make good use of your card
PS too bad we have nice PCs and not many good games to choose from, at least it has saved me a few quid from having to upgrade PC. we only seem to get crappy console ports, bar a few exceptions like Mass Effect, Fallout ...