Ranks would probably be something like this:
1. AHL
2. OHL
3. WHL
4. NCAA
5. QMJHL
It's not the sort of thing that can be "ranked", really.
The AHL is a professional men's league... players anywhere from 20-late 30's, some who have played in the NHL, many who will play in the NHL. Teams are affiliated with NHL teams for player development. It's like AAA compared to Major League Baseball. The calibre of play in the AHL is only bested by the NHL itself. (Well, or some of the top European pro leagues, but that's outside the scope of this question).
NCAA is the next higher age bracket, so it's safe to say that it's probably the next higher calibre of play, with players typically 18-23 years of age (some few 17 year olds, some 24,25,26 year olds chasing their degrees a bit later). Even in Division I NCAA hockey, though, there are some schools with much stronger programs attracting much higher calibre players than some of the other programs. But as a generalization, the age difference would be enough alone to rank the NCAA as a higher level of play than junior hockey.
The Canadian Hockey League is made up of the OHL, WHL, QMJHL. Players 16-20 mostly. If you had to break it down league-by-league, I'd say the WHL is probably on top, featuring better coaching, tougher defensive play, and more physicality than the other two leagues. In past years folks would also probably have ranked the OHL ahead of the QMJHL, but I'm thinking the gap is closing a bit there... both leagues are a bit "looser" than the WHL, but I think the Q has closed the gap somewhat by increasing their presence in the Maritimes and balancing out their style of play somewhat. Sweeping generalizations, though... as the Memorial Cup shows, the best teams from any of the WHL/OHL/QMJHL compete on very equal footing.