Pretty much any high-speed combo fighter. I think I must have finger dyslexia or something because I just can't get the flow of "see enemy starting such and such attack, identify what will block/counter it, rapidly batter a 10-button sequence into the console" down pat. It's infuriating to get repeatedly beaten so often by someone who's nerdgasmed over it practicing and learning this stuff (much as I do with sim-racers) and sucked the fun out for other people (which is why I tend to solo the racers, or only multiplayer with the stock car list).
If I'm forced into taking part (thankfully rare now i've convinced most beat-em-up kings i know that i'm not interested) then proceedings may well end in physical violence, possible a chair broken over someones head - counter THAT.
The slightly more older-school, slower paced ones, I can just about handle. Soul Edge/Soul Calibur are enjoyable. SF2 is sort of the limit... I can at least pull off most of the specials; but SF2 turbo with the speed turned up? Tekken? Or even IK+ on anything more than "swift"? Naw. Not happening. SF3 or later, or Capcom vs anything is DEFINITELY a non starter.
Sort of crap at the rhythm-actioners (DDR, Guitar Hero etc) but I maintain that's just sheer lack of opportunity and practice (and a flabby ass), and it's not utter hopelessness. Just unfamiliarity. I've got the rhythm and the melody. Odd, when you'd think that it'd be related to the fighters. Much the same button sequences anyway.
mediocre at extreme sports things and strategy/management sims (including even stuff like battle stations on facebook, or old maxis/microprose stuff). goes well for a while, but sort of falls flat when trying for the higher echelons.
competent with shooters, if not all that brilliant. can work as part of a CS team, say.
and i will wipe my own ass with your broken, crushed ego-corpse on racing or dogfight sims. i do however get a bit annoyed that the controller can't properly give the full feedback that you'd have behind the wheel/stick and make the occasional dumb mistake when e.g. misreading how much traction there is and trying to push the wheel "further" when it's already against the stops.