Dr.Brawl
Smash Ace
I agree with with lower players not understanding why he is the best. I don't believe that MK completely destroys Diddy in the air though. The problem during this match up would be more or less what happens if Mk gets control of the bananas. Diddy quickly runs out of options.Lower level players will never and can never understand why Meta Knight is a good player so explaining this to you is a complete waste of time. In order to understand why he's good, you need to learn the game at a higher level and understand each part of it. Then you can see that Meta Knight either dominates in that area or does well enough where he can use his dominance in all the other areas to make up for what he lacks in a specific area. For example, Diddy's Bananas allow him to dominate the stage and control ground moment. This makes his zoning to ground base character weak to bananas or unable to deal with them as effectively unable to compete with him on the ground. Meta Knight on the other hand has his aerial surpremecy, priority, and reach over Diddy Kong which allows him to go a little better than even with him.
http://www.youtube.com/watch?v=g2NWH82em64&feature=related