Depends on the country and how far back you are. I had a two wheel cart I won at a dinner, but wound up buying a single wheel called the Carryall Buddy or something like that. Far superior for brushy country, narrow trails, and sidehilling. Contact info is at end of the following thread:
http://www.ifish.net/board/showthread.php?t=177311. I found their phone number on the internet or called info for La Pine OR. They went back into production as of last summer or fall.
If you google around you will find an elk hunting website that compared a set of carts. They really liked a single wheel design with a low slung rigid frame made in Boulder, MT. I wanted something that could fold up and go on a packframe. The carryall actually slides below a cot I have in the back of my pickup.
Having said that, I often use a sled, a backpack, or meat bags slung over a mountain bike. Just depends where and when I'm hunting. That Carryall is a well-made and thoughtfully designed product, though.