Is a persons interest in developing skills more important to long term success than whatever natural talent may be?
I think a person's interest is probably the most important factor. If you don't have an interest in whatever you're doing, you won't last, talent or not. You could be a brilliant pianist who just "gets it" and can play Chopin like nobody's business, but if you don't care about music or wanting to perform, it's pointless.
Sometimes stars can align and someone who is naturally talented in an area (mechanics, artists, musicians) also enjoy the field their talent lends itself to. In that case, the passion and interest helps them build on top of their natural talent, or augment/enhance it with the thirst of learning more.