I do not believe I ever read the Immortality series. He has so many books, I would have to be very dedicated to read them all....
Anyway, I was pondering the WoT series in relation to Mistborn and Elantris and came to a revelation....
Most hero-fantasy novels, or even just hero-fiction novel in general follow a formulaic bent. For example, in many books and movies, there is the simple farm boy, or McDonald's worker or whatever who gets swept up and saves the day/becomes king etc. There are variations to this but pretty much this is how it goes.
The Wheel of Time follows that formula, initially. and branches out with similar things happening to princesses, etc.
Brandon twists that formula a little bit in Elantris and Mistborn. In Elantris, the heroes are the princess pawn and the heir to the throne who is reviled by his father. Mistborn has a similar theme, with one of the main heroes being the heir to the most powerful nobel being reviled by his father.
But there are striking similarities between WoT and Mistborn in terms of progression. In both series, the beginning hero/heroine starts out with a small group, and the cast of charachters gradually expands. But what is rather unique is that both series do not just expand the cast, they make all of the main and sub-main charachters dynamic. There is little of a charachter doing something out of characnter to progress a plot point (as has been the case on the TV series "Heroes" this season). Many books and authors introduce a great many charachters, but rarely do they make them dynamic, and rarely are we treated to an in depth look at them.
And I believe, ultimately, that is one of the reasons Brandon was annointed to finalize this series. His writing is obviously heavily influenced by the works of Robert Jordan, add to that his obviously great imagination (seriously, who ever would have thought about swallowing shaved metal as a magic system?) and his tenacious attention to detail. And Brandon could very well be "the next Robert Jordan".