yeah i'm pretty good, I can pick up pretty much any game any genre and master the mechanics in a matter of minutes, but then i've been gaming for longer than most people on this forum have been alive. As i've played hundreds of games over 20+ years i've gained an almost 6th sense for what the developer has done with the game and what to expect from the controls, the environments, the mechanics and even the character interactions and story (genre dependant).
However gamers do approach games in different ways, and may even approach different games in different ways. For example I played and completed the Bioshock games on easy and I'm glad for it, I think it improved my experiance of the games; at the same time i've just put several hours into Deus Ex HR on the top difficulty which I selected without hesitation knowing that that would give me the most satisfying experiance.
As for competitive play... I'm average at best, genre dependant. FPS is probably my best competitive genre but I'm a gaming enthusiast not a competitive FPS entusiast, so I never put too much time into any one game, in fact i'm usualy playing several at once and need a new game fix every few weeks... so given that, i'm never going to be putting enough time into any one game to be truely competitive in it. I've a lot of raw skill, but just not much inclination to put in the hours necessary to become truly competitive.