Actually, quite the opposite. 360's best are all coming to PC while PS3's are not.
Of all 360 exclusives, only Dead Rising and Ninja Gaiden 2 didn't come to PS3 or PC. Gears 1 came for PC. Gears 2 and Fable 2 will come out. Mass Effect is out for PC. BioShock came for PC and is headed to PS3. Alan Wake is confirmed for PC too.
Now on PS3 front:
Resistance 1 & 2 are not available for PC. Just like Uncharted or MGS4. LittleBigPlanet is PS3 only. Killzone 2 is PS3 only. FFXIII and FFVersus XIII are PS3 only.
And then, there are the best games that are multi:
Fallout 3
Bayonetta
Street Fighter 4
Mercenaries 2
Soul Calibur 4
GTA4
Mirror's Edge
Brothers in Arms 3
Along with Spider-man Web of Shadows, MK vs DC, Silent Hill 5...
PC's biggest exclusives: Diablo 3, StarCraft 2, Crysis Warhead
Wii's biggest exclusives: ... uh... Mad World. (Unless you want another Mario / Wario game)