I liked the first trilogy of mistborn but lost interest in the sequels. There were parts of the first trilogy that .. well, were better than others.
I think the Stormlight archive is Sanderson at his fantasy best. Characters driving plot in a cohesive, complex world. Stormlight has huge tombs of books covering a story that feels like it is really moving and subplots that tie back and resolve.
Of all the authors I'm following right now I think Brandon is the most likely to complete his "work". The guy is a machine for writing, he's never let a year pass without a new book.
Of course death/accidents can happen to anybody, but I can't imagine he's going to suddenly drop his output, given how prolific he has been over recent years.
One of his nice tricks is to "relax" by writing different kinds of books, which seems to be working out really well for him.
I conciously avoid reading incomplete series, with only two exceptions and he's one of them. (The other is Steven Brust, who I've been reading for 20+ years. Slowly getting closer to the finish-mark there, the waits between books aren't as bad as with some authors, but they're still annoying!)
I think the Stormlight archive is Sanderson at his fantasy best. Characters driving plot in a cohesive, complex world. Stormlight has huge tombs of books covering a story that feels like it is really moving and subplots that tie back and resolve.