It's not that Hitsugaya is weak, I think he's just depicted in a lot of the episodes as someone who completely overpowers his opponent. It really all comes down to how the plot-line and animators depict him. Hitsugaya is my favorite character in Bleach, but it's kind of obvious that, while he's got the most guff with Aizen he'll probably get owned and Ichigo will pull off the Naruto/Goku win.