Play other people's games
^ This, this, and a little more of this.
If you want to be a great musician (or even a proficient one), you need to listen to music - lots of music, and not just the kind you want to make.
If you were going to learn to play a guitar, you'd maybe get an instructor, or watch loads of tutorials online, practice, learn some songs. One day you go to an 'open mike' night and play something you learned. You stumble through it. You practice some more. Meet some people and form a band - you play at a friends party. You weren't great but you got through it. You practice some more, maybe get a different drummer or add a saxophone. You audition for gigs. You get turned down a lot and then somebody says yes. You give it your all and somebody in the crowd likes what they hear and talk to you. Now you've got a steady gig playing weekends down at the local pub.
I forget who I read that wrote comparing game development to learning to play an instrument, but having spent a few years learning to play the guitar - it's a very apt analogy. You don't start off being 'good at it' unless you're one of those very rare 1% of 1% of people. A writing teacher of mine went to a small seminar with Stephen King. One of the things he told her was, "Your first novel or two are going to suck. That's ok - get the suck out of your system." (not those exact words, but the gist of it, anyway).
Finally, you've picked the HARDEST genre of game to possibly create. You'll hear loads of people complaining about the gaming industry and things like EA pumping out a sports game year after year and how much that sucks and yadda, yadda, yadda. Guess what? The people spending money every year to buy them don't think those games suck. In fact, they enjoy them very much. First person shooters are another one - sequel after sequel. With both of those - the mechanics are the game. Graphics need to be good (that's always true, even with a 2D game), but there's not a lot of dialog between the 'hero' and the zombie hordes as your picking them off one by one with your BFG.
In a role playing game the mechanics are a small part of a much larger pie: You need to learn to write a screen play (the closest fiction writing to a game - comic books are close, too), develop characters, dialog, scenes, plots and subplots, convey emotions... Choose the right music - or even create your own. Develop a system of risk and reward so the player feels like his character is growing stronger, while the story keeps making her situation worse at every turn. And you've got to find a way to make your game seem different from all the others out there - 95% of which are all telling the same story (The Reluctant Hero).
So play games. Lots of games. Takes notes while you're playing - what do you like? What don't you like. When you're finished playing, go back over those notes and try to figure out WHY you liked or didn't like certain things. Was it a 'don't like' because it was bad, or was it a part of the story where you weren't supposed to feel comfortable? Did things seem too easy or too hard? Did you feel 'lost'? Find the precise moment you started to lose direction and figure out WHY.
Do this over and over and over...
If it were easy, everybody and his dog would be selling video games and living the good life...
