Arrow is set in the fictional Starling City and it's a major hit.
Major by CW standards, maybe, but while I haven't seen the show, would it be fair to say that Starling City is more or less TDK
It wasn't that long ago that only DC films were succeeding and Marvel films were either nonexistent or dismal failures. So even if that were true, it couldn't be said to be a causative factor in the respective success of the film adaptations, because in that case one would consistently do better than the other across all time.
Ah, but you don't need modern CG effects to do a Batman or Superman movie. (Which, correct me if I'm wrong, were the only live-action successes DC movies had
before our modern era.)
But how do you show Spider-Man swinging through skyscraper canyons without CG? How do you show the Iron Man suit blasting around and firing rockets without CG? How do you make a ten-foot, photoreal Hulk share a poignant moment with a human costar without CG? How do you do epic mutant-on-mutant battles without CG? You just don't, not in live action, at least.
You may say it's a coincidence that Marvel movies started getting good pretty much exactly when the technology to do their characters justice became available. But I think it's just as likely that, Supes and Bats aside, modern CG created a fair playing field... and that's exactly why Marvel movies are making DC look like the guys the Harlem Globetrotters run circles around.