A 37" vertical leap for a guy who is 6'5" 290# is absolutely incredible. MJ was an inch taller and about 70# lighter. That's a huge difference.
The weight makes a difference but LeBron James is about 270 and has over a 40" vert. Height has nothing to do with vert.
2013 NFL Combine Results - Defensive Ends - NFL DraftTracker - ESPN
There were defensive ends this year that had higher verts than Watt at the combine so I don't get all the hoopla.