Stephen King's Dark Tower series is my go-to epic fantasy. I'm about to start a 4th trip to the tower once I'm done with my current listen.
Enders Game by Orson Scott Card, and a select few other books in the series (Speaker for the dead and Enders Shadow most notably) - Card at the top of his game is fantastic, I just wish he didn't dive completely off the deep end.
Tangentially, Berserk, if you include manga. Hands down my favorite piece of media altogether.
When I re-read Ender's Game as an adult it felt pretty mary-sueish the second time. I got why I loved it as a kid because the smart socially maladjusted kid (omg he's just like me) was kicking everyone's ass and being great at everything. As an adult it seemed a little much. Then again maybe I'm just projecting the hatred I have for my past self onto the book.
I can get that. Its the parts around him being a Mary Sue that work so well. His ultimate draw towards pacifism despite his clear knack for death. I feel like it captures a bullied, maladjusted youth with a clear talent pretty well, all considered.