PC has more precision by default, controller can never match it. It's partially combatted by "aim assist", which PC players despise.
I can usually jump either way, but Mass Effect felt like poo on 360, and I loved it on PC.
As for the MW, I loved COD 4 and MW2, but I've never even played 3.
I've got black ops for the 360, but I've never played it, maybe I should dust that machine off.
Never really enjoyed the MP component, I'm more of a story player. I remember with MW2 in specific, being annoyed that the multiplayer and single player were separate clients, but you couldn't just buy the one you wanted.
Never realized it was the single player experience that would end up on the chopping block.