I laughed my head off when Tetris came out. I then spent an hour on my Apple II and wrote my own version. Then I played it. Shit it was good.
I was at Psygnosis when the guy who wrote Lemmings came in to collect his first royalty cheque. That started as an exercise for his graphics artists, how small can you get a sprite and still animate it. The cheque was for just over £1,000,000.00 and they owed him another 900k, but they said he may have to wait a week for that.
"The Gadget Show" a UK TV program ran an exercise. Two presenters designed iPhone apps, one created a simple bike game. It sold over a million copies.
Angry Birds is a trivial piece of code, hell you can do your own version in a few hours with Box2D. Look at the sales figures for that, action figures, mouse mats, blah, blah, blah.
Can you write a successful game now? Hell yes.
If the idea for the game is good enough, and the graphics / sound effects well done, the skies the limit.
In fact now it's probably easier to write a game than it has ever been. I had to work in assembler, had to port my game to multiple platforms in assembler as well. Now you can work in high level languages, get multi-platform engines, etc.
All this makes it a hell of a lot easier to get your idea from inside your head, and out into the world.
Of course because it is so easy, there are loads of people doing it, so your idea needs to be damn good.
Is an RPG the right way to start? Probably not.