Wait, it's possible to be good at arcade games? :o I'd say I'm best at fighting games, but mainly Mortal Kombats and Soul Caliburs. Even then I usually lose to many players, though I try to put up a good fight. I've yet to really get into Tekken, Street Fighter, and so on. I still have no idea how I haven't played a Bloody Roar yet.
Otherwise, I think I'm okay at Centipede and Dig-Dug? The Namco classics are legendary and a ton of fun, but I can't get much farther than a couple levels at most of them. I used to be dece at Galaga when I had Namco Museum on the N64, getting to around 10 levels in IIRC, but those skills atrophied hard over years of neglect.