Actually, make it Star Fox 64. I've played it way more than Xenogears (and the multiplayer was damn fun), but it was a really tough choice since I like them both equal I must say! One is a single-player game while the other one is fun to enjoy with friends (even the single-player). ^_^
Random game thought :
Why is Bionic Commando Rearmed 2 getting so much hate? We finally get a real game and they're not even satisfied... I'm starting to hate the gaming community so f****** much...