Graphics = Killzone wins here.
Story = Ok I don't think anywone knows the entire story for killzone 2, but chances are MGS4 will have the better story so....can't say.
Characters = While I can't say for certain, no one in my book can beat the cast of MGS series as a whole. There are characters I like more, but everyone in that universe flows wonderfully together
Online = This is a matter of opinion. MGO online is a complete different game from Killzones so it's an either or. For me it's a hard desicion. Killzone will keep me in for a long ass time but MGO drags me back in every month or so.
Gameplay = Read above. TPS Stealth game vs FPS action.
Sales = Honestly no fucking clue. MGS4 did extremely well and has a moderate fanbase while killzone has a small but dedicated fanbase, however can attract more people since it is a FPS. With ps3 recent game sales I'm thinking MGS will have a slight edge, however the probability of me being wrong could be high.
CURRENTLY PLAYING: Warframe, Witcher 2
