Although Alaska is vast, the state has fewer miles of roads than the state of Rhode Island. The road system is readily accessible from the larger cities of Anchorage and Fairbanks. While it is possible to hunt off the road system, there is a lot of competition for available big game and hunter success rates are generally low. Hunting success rates for hunters using ATVs are generally higher than for those using only highway vehicles, but are still relatively low. I believe this is because many people spend more time running the machine than hunting on foot once they reach their hunting area.
Boats are another option along Alaska's river systems.
Where access to launches is within easy reach of Anchorage or Fairbanks, there is a lot of competition for game among boat hunters. The farther you are willing to run from a launch site, the less crowding you are apt to find. Chartering an aircraft for a drop-off hunt is what many consistently successful Alaska hunters prefer. The upfront cost puts off many new hunters, but in the long run the costs are reasonable given the solitude, high hunting success rates and the sheer adventure of the flights and landings themselves. Some of my most memorable hunts for sheep, bears, moose and caribou have been fly-in hunts.