i've only played 1, 2, and CoM on the gameboy, and i think CoM actually has the best gameplay of the three.
1 had a bunch of problems, and while 2 fixes lots of them, it's just too easy of a game. CoM felt pretty good once I wrapped my head around it.
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XS2 is the only good Xenosaga game - Lady Ashe
http://backloggery.com/cwistofu