Just as well, beating X1 is impressive, as he was able to capture Luke with only a group of stormtroopers, and they definitely weren't the ones who put up the fight.
Granted, this was shortly after Luke defeated Vader, so he wasn't the All-Powerful Grand Master as of yet, but by that point he had already fought Vader in ROTJ, which makes it impressive that X2 defeated him. It's also revealed that X1 was trained personally by Vader in the force.
Just as well, he had also fought off Vader's personal Guard on Bast Castle, and at least a dozen of the Emperor's Personal Guard (red-cloaked guys), while still a clone/rebel.