He's a gifted mimic and as such he's done some really great pastiches.
I love Sandman, but I think it's overhyped as well. It routinely places first on lists of the best comic runs ever, which IMHO greatly overstates it. Also, the average Sandman fan thinks Season of the Mist is the best Sandman story arc, when it's like, fourth out of seven or eight actual arcs, making it really just average Sandman fare (behind Brief Lives, A Game of You, and The Kindly Ones).