Here are some of my choices, these are just my opinions.
Wrestlemania 21 - Main events were not that good and the rest of the card wasn't that good except for Kurt Angle vs Shawn Michaels and MITB which both stole and saved the PPV.
Wrestlemania XII - Except for the Bret Hart vs Shawn Michaels match the card wasn't that good.
Wrestlemania IV - Matches weren't that good