i'd say that i'm more for the PC flag than anything ...but its kinda close.
after that ...probably xbox360 followed closely by the ps3. they're both pretty even, tho ...but i guess i'd say that i prefer the xbox over ps3 just slightly. mainly because the mutliplatform games tend to be a little more polished on xbox and i like xbox live more than psn as an online service.
oddly enough, tho, my two favorite games this gen have been ps3 exclusives - Demon's Souls and Killzone 2.
can't wait for Killzone 3, btw.
nintendo comes in a distant 4th after the ones i already mentioned. i do enjoy nintendo's own exclusive titles, tho. stuff like New Super Mario Bros, Mario Galaxy, Zelda, Metroid, etc ...those are all great games. its the 3rd party support on the wii that's rather lackluster, imo.