(Cats in the Cradle)
That's a tough one. This is a really good cover, updated for a more modern audience, but I really like the original.
Here's one that is so different from the original that it's really tough to say which is 'better':
The Cardigans - Iron Man
I love the original, no doubt about that, but I often prefer listening to this one. It's really relaxing! I love a cover that totally reinvents the song, and this one definitely does that.