With regard to some of the early WM's I thought some of the tag team matches were the best shows of the card. For example, I have a real fondness for the opening match of III, Martel/Zenk vs. Orton/Muraco. The tag team title match from the first one is great too.
For all-time great though I'd have to go with Hart/Austin. That was the real passing of the torch to Austin, any lingering doubt there may have been that he could be the next guy must have gone away that night.