The reason you can't use g25/27 etc on the 360 is due to the way the 360 does FFB. IIRC PC's can do both kinds (forget the names) but it's essentially Computer based FFB, or Controller based FFB. IIRC, the 360 uses controller based FFB, whereas the g25/27 use computer based.
It's something along these lines, i was reading up to see if i could use the g25 with the 360, sadly i cannot. There isn't even an addon/inline control system. So i think you're stuck with either the fanatec(i THINK these work with the 360?) or MS wheel.