There are other reasons, but I'll just pick one.
I absolutely love how Obama calls the Republicans on their campaign bullshit the way Kerry and Gore didn't. When he said in his nomination acceptance speech:
"They make a big election about small things."
I shouted "YES!!!" It had been that way since 2000 if not before, and it was obvious to anyone who had paid attention, but it needed to be said, and he said it. Barack Obama speaks for me.