Different games teach different skills to different degrees. This is not because some games are bad and others are good, it's because games are different. They reward certain things and make little use of others. And more, they do this in a very obvious way. When you go to a convention, it is REALLY easy to spot the person at the table who has never left the nest, and has only ever played variants on D&D or Storyteller.
The heartbreaking part is that you most often encounter these folks when they've decided to stray off the reservation and try some new game. Sometimes this goes well, but most often, it just ends up reaffirming their suspicion that other games suck. This is not necessarily because the new game is bad, but rather because the new game is, at least in part, effectively in a different language of play than the player is used to, and they find themselves put on the spot. Unless the GM is very sensitive to these blind spots in new players (something that's rarer than it should be), the players will end up frustrated and feeling foolish, even if they're perfectly capable.
To put it more concretely, if you've only ever played D&D and you're dropped into a game with, say, strong scene framing, you may not be ready to frame a scene. Not because you're not smart or not creative, but because this is a new idea. Your frustration will be roughly akin to trying to cook a microwave meal where all the instructions are in Russian, all in front of an audience. Even if you manage it, you'll be self-conscious and feeling foolish the whole time. This is not the kind of fun experience that bring someone back to a game.
That is a problem, because the simple reality is that after a certain point, nothing is going to be as useful at improving the games you love as learning other games. Even games you don't like.
I don't like Burning Wheel much, but despite this I own every damn book that Luke & company put out. This may seem contradictory, or like some kind of reflexive indie purchasing streak, but there's something more to it, something that I consider very important.
See, not liking Burning Wheel as a matter of taste - I play it, and it doesn't really get my motor going - but at the same time it is a really good game. Just a small amount of time spent reviewing the products (especially self-contained marvels like Mouseguard) makes the quality of the work obvious. What's more, even if you can't see that, Luke's passion is clear both in and out of the game, and I can point to no shortage of people who have had really excellent experiences with the game. Any one of those things would speak well for Burning Wheel - all three of them together more or less shout.
There are two reasons this is important. By decoupling my dislike from my judgement of the game, I'm able to appreciate it's strengths and discuss it with people without pissing all over it. This is such an obvious benefit that I would not even feel it worth mentioning in any context but the internet. Second, it leaves me in a position to learn from Burning Wheel. This last is the reason I consider my position to be something other than hippie or zen - it's _greedy_. The world is full of games, and even the ones I wouldn't want to play are full of things I can learn.
Now, I can learn a lot just by reading the text, but there's a bit of chicken and egg to this because the more different games you play, the better able you will be to create a picture of a new game from its text. So I guess that means I've had to play a lot of games to not need to play some games.
But as nice as that is, it's still not a substitute for playing these games, or at least giving them a go. This means that it's worth your time to spend some time playing games you can see the virtues in but which may not be to your taste. By doing so with open ears and an open mind, you can learn a lot of things that can make the games you like better. You don't need to keep playing them - just take what you like and see if it an work back in the game you know you like.
That's a pretty simple proposition, isn't it? Playing other RPGs than the ones your comfortable with can teach you new things. You wouldn't think it would invite as much opposition as it does, but there it is.
I'm not proposing that you rush out and grab a copy of Everway or Posion'd just because they're obscure or indie. Look at the books. Read the backs. Find something that makes you think "Oh, hey, that sounds cool", then give it a try.