There are a couple of games on the 360 that can be played with PC gamers at the same time, Shadowrun and Final Fantasy XI and that's only because Microsoft have something to do with both.
The problem is with the coding of the games, it would be too difficult to code the games to work with each other across different formats. Another problem is custom content. PC users can add custom created maps and different weapon skins all of which would not be available on the PS3 causing more problems.
That's my long answer essentially saying No