I think the RP I'm currently GMing would make for a decent novel. It's shaping out very nicely, if I do say so myself. But other than that, I think what people forget is that RPing is NOT writing a novel.
I think some people are trying to slave over every single post instead of viewing the whole writing process as fun, not work, and having inspiration pour out of their creative mind. Once you learn how to differentiate between work and play, you'd be surprised how much you can enjoy writing long ass RP posts.