Use Blender www.blender3d.org ITs 20000000 times better than GMAX, personally i think its better than real MAX, but thats just me. Its free, open source and easy to use. Just as powerful as a commercial program, expecially if you modeling for games.
If you must use gmax, than your out of luck. GMAX is for mods, and the games that use it have to pay Sutodesk a license for GMAX support. So you wont be getting any legal exporters that Autodesk doesnt give permission for.
If you must use gmax, than your out of luck. GMAX is for mods, and the games that use it have to pay Sutodesk a license for GMAX support. So you wont be getting any legal exporters that Autodesk doesnt give permission for.