PC has less hackers than either of the console versions thanks to dedicated servers and I can honestly say from experience that the PS3 version of the game is virtually unplayable due to some serious input lag which is almost a full second behind you. Don't get me started on how bad the textures look. Not only that, the Call of Duty games pretty much starting with 2 have been pretty dumbed down garbage as far as multiplayer is concerned, though the PC version of 4 did have some redeeming qualities thanks to mods. It should also be noted that your not stuck with keyboard and mouse in the PC version if you don't want them, you can easily use XPadder (which works with virtually everything you can plug into your PC, I actually use my Gamecube controller for Touhou games) to map the controls to any gamepad you want and there's actually profiles made specifically for this game and the Dual Shock 3 and XBox 360 controllers on their forum.
As far as multiplayer alternatives for BLOPS 2 is concerned, I'd recommend Killing Floor (which takes next to nothing to run and goes for cheap), Battlefield 2 complete (a ten year old system can max this) and Battlefield Bad Company 2 (about the same requirements as the CoD games after 4), the Counter Strike (take next to nothing to run) games, and Urban Terror (a fifteen year old system can run it on max, this game is also free). You should be able to grab a handful of what I just listed for the same amount of money you would spend on a single copy of BLOPS 2.
ECKZBAWKZ HUGE LIST OF ACHIEVEMENTS GOES HERE....
Oh wait.