Of course I have seen New frontier
and that was a rare exception. Even than it was based on a modern retro style comic.
Superman will have been in publication for 75 years in 2013. There is much more material to draw upon than they have. There are a lof of great "imaginary stories" from the 60s which would make great animated movies.
Curt Swan had the longest run of any artist in Superman's history. I would love to see animation in his style.