Why don't I like Stephen King's novels?

Ok I love horror fiction. I read everything I can get my hands on by Richard Laymon, Jack Ketchum, Ira Levin and various others but I just don't dig Stephen King that much. His stories seem to be drawn out, which is not a problem if they are good but they're just not. The books he wrote as Richard Bachman I like, actually, and a few others. I liked Christine, Gerald's Game, The Long Walk, Rage but I tried reading Desperation and it was incredibly boring. One of my best friends is obsessed with the Dark Tower(s?) series and suggests I read this and related books, but I am always so disappointed, any advice on why I don't like it or maybe a reason to give it a shot? The phenomena in his books is never explained and some people may find this endearingly ambiguous, but to me it's just the sign of a bad writer who can't finish his own ideas. I don't want to anger anyone, I just want to understand and maybe I can enjoy his work. Who knows?