I have a lot of problems with Superman Returns, but Routh was not one of them. I thought he was fantastic and would really hate to see him go. I even loved Kevin Spacey. Kate Bosworth, however...ugh.
I'd really like to see Singer get his chance at The Man of Steel. After Returns, the studio will keep their eye on him and make sure he sticks to the script
, which is what was needed on Returns. As long as he has a leash on him, and there's a fantastic script, I think Singer would make an incredible Superman film. Just don't let him shoot every whim he has during production and convince an editor with things that completely muddy the themes.