I don't think Quesada is ruining Marvel per se. I do think he provides creators with too freer hand in regards to what they are able to do with characters. While this approach has led to a great number of good things happening, I think it has produced more misses than hits. The same could be said of Didio's tenure at DC though.

What I buy is a pretty evenly split between the big two, with Astonishing X-Men, Blade, Captain America, Daredevil, Iron Fist and Uncanny X-Men from Marvel and Asto City, Brave And The Bold, Green Lantern, Justice, The Spirit and Superman from DC plus the B.R.P.D. and Hellboy books from Dark Horse.

Astonishing I should have given up on long ago, Busiek's run on Superman has been less than impressive so far and Green Lantern is starting to become an "all style no substance" book - but an in depth into why I buy books is something best saved for another thread.