Gosh, I have a lot of covers that I like better than the original, so I'll take a couple of the more recent ones that've caught my eye. So, Alien Ant Farm is one of my favorites too, but I also love the rock/metal covers of Disney songs by Jonathan Young and Caleb Hyles. Particularily their rendition of the Prince of Egypt soundtrack (disclaimer: I know that's not Disney), but the greatest improvement for me is made by Youngs' rendition of Evermore from the live-action Beauty and the Beast film. He gives it the skind of depth that makes my ovaries eplode.
3TEETHS cover of Pumped up Kicks. I like the original and it could be argued that the upbeat tone of it is what creates the memorable lyrical dissonance but I also like THIS. It gives a very happy-sounding melody an industrial, almost Marilyn Manson like reworking, essentially making it a completely different song.