Just to take it further to top non-NHL prospect by position
Johnsson - Brooks - Kapanen
Dermott - Liljegren
Woll
LW is a bit of a toss-up depending on how you'd measure the ranking: likelihood to make the NHL? ceiling at the NHL? Likelihood to make the Leafs under Babcock?
Along with Johnsson, I'd put Grundstrom and Timashov there as options, but both of them have a smaller body of work with the Marlies. Rychel, while currently probably better, is, I believe, pretty much at his ceiling (4th line with a pop of skill occasionally).