[Jeritron]

I don't see how The Dudleys were a bigger success than RVD.

I agree that they were very successful, but they were far more watered down than RVD, if you're familiar with the original ECW product. They were massive heels, and functioned like the Two Man Power Trip or nWo in ECW.
In WWE they were way over, but they didn't draw heat that way and for the most part they were over for table spots. Fans wanted the tables and there was very little substance other than that. They were always a gimmick tag team, and for a lot of their stint played the supporting role to E&C or The Hardys in the midcard. You never saw something like The Dudleys fueding with the likes of Stone Cold and HHH in the main event, which would be commonplace in their ECW capacity.
In ECW they were a main event draw and a powerhouse on the microphone/storylines, despite being a tag team.

RVD was constantly a singles star, and had a lot of great matches. He may have taken it down a notch in the ring, but he still busted out his classic offense and he was over for the exact same reasons he was in ECW.
He may have been "cooler" and more of a cult favorite in ECW, in some people's opinions, but he was more successful in WWE. He was consistently over for years until he won the WWE Title off of John Cena.
I don't see how much more could be expected out of his run outside of ECW, other than wishing he'd go coast to coast a bit more often.