It has nothing to do with not being emo. And considering his tendency to cry, calling him not emotional is quite ridiculous.

I love Zidane from FFIX. He was cheery too. But know what makes him and Tidus different?
Zidane never did anything mind-numblingly stupid.

Did Zidane ever walk up to and start sniffing one of his party members? Nope.
Did Zidane ever grab a megaphone and embarrass all his friends by being a total spaz? No.

But in the end, I don't hate Tidus. I sympathize with many of his issues. I just dislike a lot of the things he does.