Mustrum_Ridcully
Legend
Another advantage to being good at game design might be that, even if you don't make a best-seller, other game designers might take notice and hire you.
Mike Mearls did a great job with various games, and now he works for WOTC.
Basically: If you want to create your own RPG and be successful as D&D, be a good game designer, get noticed and become hired by whoever owns the D&D brand.

Of course, you probably still have to get the rest of R&D out of the way to keep them from mucking up your game...
