I really like the one that won the Iron Man contest. That's pretty cool.
Same here. I also like:
Fernando Lucas' concept for the Superman crystal suit. The comments that the execution looks like a chicken suit are on-target, but with a different execution, the idea could be very original. The Superman entries are too samey (and what's with the Keanu Reeves "Jesus" one?
Daniel Krall's more "traditional" take on Wonder Woman - less extreme than the other ancient-Greek costumes, which start to veer away from the idea of her being a modern superhero character.
They shouldn't have bothered with Rocketeer. That is already a very well designed character and the entries really didn't diverge much from the original.
They should try someone like the Sub-Mariner or Ant-Man next. Or Daredevil, there's a guy in dire need of a makeover!
For a real challenge: tackle Batman.