I'm only counting them as their own platform since you can play them on a PS3 web browser... and browsers on phones, tablets and other devices with a web browser and support for flash.
Although they are made for the PC and are buggy on a lot of phones.
Reasons why PC gaming is still amazing...
PC's are the most powerful platform for gaming
Most console games are already on the PC even if alot are now just ports.
big upcoming games like Battlefield 3 for the pc
RTS like starcraft 2
the vast number MMO's like
the range of indie games, such as Minecraft
game mods and customizations.
In my opinion Facebook games and browser games count as their own platfor...
Battlefield series for PC is defiantly the best! can't wait to get a copy of BF3