I consider myself a well skilled gamer. I play pretty much every genre of games except for RTSs (I just can't get into them) and music games (I like playing Rock Band with friends but not by myself).
Bayonetta was really the first hardcore beat'em up game I played, and I was able to get good enough to play on the highest difficulty. The dodge offset mechanic really won me over and kept me playing.
If it's an online game, I really try to get good at it and I normally do. However, I don't play that many online games unless I really like the game mechanics. I've played Metal Gear Online for over 3 years and I'm very good at it, not best player but I can hang with the best. I really got into Warhawk for a time and loved it. I got really got into the MAG beta and loved it, just never picked it up. I don't play games like COD (I did play COD4, which was my first online FPS experience) because I hate health regen, moving spawns, unbalanced gameplay, matchmaking, etc. and most online games have all the features and mechanics I don't like.
I get hardcore into baseball games. I can play MLB The Show on the highest difficulty, and I win about 75% of my online games.
I start every game on hard as normal nowadays is rather easy. I just got Deus Ex: HR and I'm playing it on the highest difficulty, it feels like normal to me. I do play stealthy so I don't really have to out shoot the AI. But with your powers and stuff, you can play pretty aggressive and have an easy time still; toss a flashbang and take out a group of enemies.