Doing a few spots suddenly makes someone better than Rey Mysterio? If that was the case Jeff Hardy and Sabu would be living legends.
Sure he's younger than Rey, therefore he can pull off better high spots but that doesn't make him a better wrestler. Mysterio can put on a hell of a match. He has more experience than the majority of the WWE roster so he knows more about putting on a match than most guys. Plus, in his younger years before all the injuries he could pull off some of the most amazing spots I've ever seen. Just watch Mysterio vs Guerrero at Halloween Havoc and you'll see a perfect example of why he has lasted as long as he has in this business.
It's going to take a LOT more than a few quick spots for Sin Cara to be considered better than Rey Mysterio.