unsanemaker: I use a wired one myself with PC games. Considering that this game came out in 2004 I don't think it is possible to find a mapping reference anywhere. What are the base actions on the 360 controller?
here's the thing: it doesn't matter.
for most of the game, as long as you're hitting a, you'll probably be ok. it's...not a very good game.
i'd also advise keeping your keyboard handy, because i haven't figured out what the "supers" are mapped to. [supers are moves that charge up over time and that deal lots of damage to everything near you.] - you get a team super [everyone joins in] and a solo super [for your guy you're currently controlling.]
apart from that, assuming the diagram i've pasted below:
http://img4.wikia.nocookie.net/__cb20130217165529/residentevil/images/b/b3/Xbox_360_controller_diagram.png a: hits things.
b: kicks things
y and x may as well not exist.
right bumper and a: shoot things at range [useful with the mage.] hold it down for a charge. again. good luck with not getting overwhelmed by guys while charging your attack. this is SUPER USEFUL on the spider level. [you'll know it when you see it.]
the right stick doesn't exist as far as the game's concerned.
the d-pad changes characters.
the left stick moves you around.
the left bumper allows you to shield.
you'll need the keyboard for...q? i think it is. and t? or something, i forget.
they didn't bother mapping the supers to actual non-keyboard commands, and occasionally, you might need these to clear out guys so more guys can come at you.
apologies if i have missed something important, here. i'm doing this from memory.
the conclusion i am swiftly coming to with demon stone?
"the only winning move is not to play."