Music is like sports - which is something I'm sure the vast majority of the picked-last musician dweebs in here have no clue about.
You can practice and practice, and get better, but you'll never be as good as the guy that just has natural ability for whatever it is he's doing. Take Tiger Woods for example. Any one of us could study the game, take golf lessons, and practice our asses off. We'll never be as good at golf as he is. Yeah, there are other great golfers, but he has that something inside of him that makes him dominant. Same with Watne Gretzky, Michael Jordon, Joe Montana, Pele, etc. It's the same with music. Lots of us are decent musicians. With practice you can get better. But with all the practice in the world, you'll never be as good as the guy that just has it and only half-ass practices.
And....while you can teach theory, you can't teach rhythm. Some people just can't keep a beat.