I enjoyed Eragon and Eldest, but I don't remember a thing about the third one...and even though I liked the books, and I was impressed that he published at 15, I saw elements torn directly out of just about every single fantasy book I've ever read. He's not particularly creative, he just mixes everything at his local library together and makes a story out of it.
That said, I don't think he'll be writing past the Inheritance Cycle, and it'll die off pretty quickly after book 4. Not to mention he only publishes a book every four to five years, which irks me to no end. Brandon is a newer writer, but I don't think it would take much to make him hugely popular--his is the best stuff I've ever read. I have the same problem as Wolfstar--my friends don't read. At all. I've gotten one friend to read Sanderson--and she loved it to pieces--but no one else will even try. So those of you who have book groups or make friendships because of your reading styles will probably have a lot better luck with this than I will.