Time will tell on that. I'm probably being way too biased, but ALW's works are more made for the masses and the tourists. I'm trying to think of the mainstream band equivalent where they sell tons of records because of the mass appeal, but holds on appeal to the more discerning rock enthusiast. ALW isn't without talent or without his good work. But as a whole, his stuff is meant to appeal to the non-theatre goer.
I'm a serious theatre enthusiast and I can think of few things I'd rather see less than Cats or Phantom....maybe Wicked. Broadway has become like Disney these days much to the dismay of avid theatre enthusiasts. ALW is seen as one of the first to start pushing it in that direction. Very little of substance comes out of broadway anymore, and it stinks.