Gonna have to beat the dead horse with the baseball bat and say that most of the main characters in the FF series (and some of their respective party members x.x) have made me lol with their cookie-cutter thoughts and actions ever since FF6.
Cloud gets a lil bit of slack from me because I was only around 7-8 years old when I first played 7, but with the privilege of hindsight... yeah, think its safe to say he wasn't terribly unique as far as heroes go.
Squall...ugh, from the very first few cutscenes I couldn't stand him. Think Squaresoft had some kind of formula in their character development that made the heroes' likability go down in direct proportion to how badass their final special move looks.
I actually liked Zidane a lot. Sure he was placed in the overused "underdog gets leg over royalty" bracket, but he made me laugh often with his dialogue during the game. Also didn't hurt that: A) he actually smiled, laughed, and had a sense of humor for more or less the whole game, a nice contrast from the depressing heroes of 7 and 8 and B) he was a special person (as were the rest of the party members I guess for being able to use Trance) that was "born" with special powers so that it made sense when he and 7 others beat up some villain with the power to end all life with a thought using store-bought weapons.
Tidus and Vaan thoughts have already been well explained and elaborated on by other posters
But yeah Square Soft/Enix has/had a terrible habit of designing bad main characters =/
edit: changed a typo made in the first paragraph (FF - FF6)