Just joined, saw the site from Digg.com, and I really like what you guys have got going here, especially the powers rankings and contests.
Some people have already mentioned that many of the vs. battles are decided through popularity and not really through a comparison on powers, even in the Video Tour this is evident as the commentator chose Daredevil over somebody else(I think Deadpool) because it's his favorite character. While this is simply the nature of the beast since not everybody knows what each character is capable of, I thought of two things that might help.
The first is having descriptions and images of Feats related to the specific powers, and have those available on or near where the powers for characters are listed. On the character page have the icons for the powers a 'FEATS' button or actually make the colorful icon lead to those feats, and do something similar when doing vs. battles.
These feats would be explanations of things done and/or better yet, images of those feats happening. The feats listed should be demonstrating the upper limits of the power of the character, so for Superman it'd be lifting a sea tanker, not just a truck, and for Professor X it would be of him subduing somebody like Emma Frost, and not Jonah Jameson.
The second thing would be to list Caveats to powers, to denote special cases for the usage and implementation for these powers. For instance under Telekinesis Superboy is at the #3 spot, which is correct but this is only when he is touching something because he has 'tactile' telekinesis.
It will also give you the ability to explain what things like Magnetism reall means, and what actual feats that gives the character. Take for instance Magneto, he is listed as having the power of 'magnetism'. This is all fine and dandy cause he does have magnetic abilities, but he also has the ability to move and manipulate things that are metal(or maybe just ferrous, I forget). This in practice gives him telekinesis and the ability to transform things with includes creating constructs. So by adding Caveats to telekinesis you can him to that power without complication.
I suggest to denote this change the color of the rim of the icon to something else, then in the power rankings page include the caveat to the left of the character name.