Chris Jericho, because even though many knew he was coming, that pop was huge and no one had a easier ride to WWE stardom like Jericho. I mean the WWE has tried to bring that hype for another wrestler, but it has yet to happen. That was the best debut ever and no one can compare the the countdown.
Agreed, this is the ladder of what debuts in wrestling should be like. I also enjoyed Lance Storm's in WCW, where he came out of the crowd and springboard dropkicked three count and the crowd erupted into "ECW" chants.