I think besides Batman (1989) and the Donnor Superman films, DC has consistently failed in Hollywood for reasons that are out of the hands of DC. Warner bros. has a track record of doing all they can to make a buck. I for one would love nothing more than to see DC succeed as Marvel has, but with no respect for the source material, WB is constantly kicking fans in the face.
Let's begin with the example of BATMAN FOREVER. I imagine Warner Bros. said let's sell toys and merchandise, who cares about respectable cinema? Only kids will watch this crap anyway, and if they have cool toys the movie will sell.
I had been hoping for a good vision of Batman, and Nolan came close, but let's face it, he did not utilize the Batman character as much as build up a supporting cast around Batman. Christian Bale was a magnificent Bruce Wayne but a terrible Batman, whereas Gary Oldman, Michael Caine, Heath Ledger, Tom Hardy, and Aaron Eckhart gave stellar performances as their respectable characters.
Now to Green Lantern, I will not take the easy way out and blame it all on Ryan Reynolds, although his terrible portrayal of Hal Jordan was laughable. The true flaw was in the very hokey script. In the 70's Green Lantern was a hard hitting comic book with very real social commentary, and the film had none of that. They shot for a fun popcorn summer blockbuster and failed miserably at even delivering that.
As for Superman Returns I believe again Warner Bros. were standing on Bryan Singers toes the whole time. Singer is a respectable film maker but was unable to meld his vision with what fans wanted to see. And frankly, they shouldn't have connected it to the Donner films, but just done a reboot.
I love DC and all of their characters and I pray for salvation in the hope of Man of Steel being awesome. However, if it is not a decent attempt at reviving the franchise, I believe it will be the nail in the coffin for any DC film that is not Vertigo based.