Mountain bikes work great. We use them to go up gated logging roads to bow hunt elk, etc. Sometimes the trip in is 2-3 miles and takes over an hour(where ATV's are prohibited of course), but the trip out is usually 10-15 minutes or less on the bike. We put the ATV bow/rifle holders on the handle bars too. I have saddle bags for packing a spike camp in, and we often strap deer or antelope to them as well. My father-in-law made a hitch for his game cart so he can pull it with his MB.

Here is a pic of us getting ready for a 4 mile pack into remote mule deer country in Eastern Montana:

http://eatsleephunt.googlepages.com/PackininEasternMTMuleyHunting.jpg