At least for recent games, I used to be a boss at Mario Kart 8, rarely ever getting lower than 3rd place in nearly every online match I played.
I was also really good at Smash Bros on the 3DS. As most remember the 3DS version came out several months before the Wii U version did and most of my time was spent on the 3DS version. I had a decent win ratio with Zero Suit Samus, and while I was nowhere near a pro I'd consider myself pretty damn good at that version of the game. Funny enough I'd say I'm average on the Wii U version.
I used to be able to play Star Fox 64 without getting hit. I used to replay it over and over again when I was a kid and it never got old for me. Still love the game, but not nearly as good as I used to be.
Like Star Fox 64 I used to play Tekken Tag Tournament all the time on my PS2 and was very good at it for a while. I recently played against my boss and totally noobed it lol.
In general I am pretty good at 2D fighting games such as the Capcom VS games, Street Fighter 2 and 3, King of Fighters, and other similar SNK titles. Oddly enough I suck at the ArcSYS fighting games like Blazblue and Guilty Gear, just never got the hang of them I guess.