Who said to take every character and do that? Where would the contrast be? Ah, so silly you are to jump to conclusions. Nomura is no different than any other artist, not all of his characters are covered in belts and zippers and wearing black. Obviously you turn a blind eye or just can't admit to be wrong. Kingdom Hearts is the only game in which characters were covered in those things you mentioned; at least, the only one I am aware of. And again, I feel that that was just a theme in KH.
The similarities between Cloud, Squall and Tidus are few and far apart and almost impossible to tell. But you should know, a character designer’s characters will often times look similar to one another. That’s their style, of course. Now, lets take a look at Amano. Have you noticed that all his original sketches just about never look like the one they put in the game? Not only that, but his art is so abstract that its not even appealing to look at on a game character.
And let us go into this: Cloud has no belts or zippers and doesn’t wear black. Well, maybe a belt. The original Cloud, that is, for FF7, wore one belt, around his waist; like normal people? And his outfit was PURPLE. Now, take a look at his remake for Advent Children. Only parts of it are black, the shirt itself is a dark blue/purple color, again. Purple = royalty. It also fits well with his blonde hair and blue eyes.
Squall: He was an 'emo' and 'angsty' character. I think its only NATURAL he dressed in black and had belts. Its called dressing the character how their personality is. Besides, he has 3 belts on his thigh and three on his waist; one that does make sense. It doesn’t even look like a lot!
Tidus: Again, he had 4 zippers! ALL THAT MAKE SENSE! Just his outfit looked kinda weird, so it doesn’t appear so right away, but if you think about it, they do make sense.
Cid, well he wears an outfit that looks like it belongs on an armature pilot (Blue, white and brown). Sephiroth wears black and has gray hair; bad guys wear black anyone. Oh, and too many belts and zippers? He has like... two belts and NO zippers. Do you even LOOK at these characters before you sprout things or just naturally assume they have them because they are Nomura's creation?? Vincent is supposed to be DEAD and has DEMONS in him; he is almost like a vampire! These outfits only seem to REFLECT the CHARACTER in some way. I really don’t see what you're talking about. Its almost as if you are making stuff out your butt or something.
Seriously, the way Nomura does things only adds uniqueness and originality to the characters. Its better than seeing all this over used crap I see everywhere. I like change. And its his art style. Everyone has a different art style and a way of dressing their characters. Square LOVED his designs and thus made him one of the main character designers; in fact, they said that he was best suited because his characters are animish and are easier to turn into CG models as apposed to Amano.