I would not write off the Watchmen cast as simply "mature superheroes". Watchmen (sort of, if you want to believe my interpretation which in no way has to be the correct one) parodied the whole genre, showing off superheroes in a different light, bordering on cynic. Basically the point I'm trying to make is that the Watchmen cast was not "cooler", closer to the exact opposite.
Again, not stating facts here ^^
As for the question itself. I enjoy most types, except the ones that try too hard loosing touch with what they really are. Kind of like making Lego Rock Band in an attempt to make the game appeal to younger audiences... 'cept the other way around... confusing?