do u think FF characters r the same?

[Savannah]

Ummm, those three characters are absolutely nothing alike.

I think you (and several others) missed the point of my analysis. While the characters' personalities are different, they all serve basically the same purposes in the game. I'll go into more detail:

Yuffie -> Selphie -> Eiko -> Rikku
Hyper, cheerful girls who provide comic relief and are usually the "other hot chick." These four probably have the most similar (arguably identical) personalities-- Eiko being the most distinguishable, if only because she's a child.

Tifa -> Rinoa -> Garnet -> Yuna
The strong-willed but sensitive leading lady who wins over the main males-- usually proficient with white magic/healing.

Zell/Irvine -> Wakka
The bouyant, hopeful, encouraging sidekick to the main male.

Barret/Cid -> Steiner -> Auron
The independent tough guy. Always the hard-hitter of the bunch.

RedXIII -> Quina/possibly Freya -> Kimahri
The (usually useless) non-human character.

And, another that occurred to me now:

Quistis -> Freya -> Lulu
The strong, seemingly detached independent woman.

Of course, I'm not saying all the characters within these groups have exactly the same personalities, but they're close enough and serve similar enough purposes that you can recognize the types in each game.