Don't tell me it's always because of quality. Not every book is an Alan Moore title (ie Watchmen) or an Ultimates. I dig Green Lantern, but there's no way that it should take as long as it does to come out.
I'm thinking that we're heading towards a bi-monthly model, and I'm not a fan of that. I'd rather have books come out on time, or hell, come out with fill-in stories that deal with the supporting characters and/or setting (ala Times Past on Starman), rather than wait and wait and wait.
I cancelled Civil War and am basically avoiding the majority of Marvel's output for this reason. The quality's just not there to justify it every time.
What's the solution though? Personally I'm either switching to trades, or sticking to books that will stay on track 90% of the time. What do you do though if you want to keep reading, but are getting frustrated by the delays? I'm thinking that more lead time is one solution, though getting either of the big two to enforce that seems impossible at this point.