Given perfect information, like from a video game (with access to the object model, etc), the DARPA challenges aren't really that difficult. You just have to plan a path and then stay on it.

Its the noise of the real world that is infinitely challenging. You have to incorporate probabilities into your decision making, which is much more difficult. Jumping a mario around is much more AI intensive because the amount of solutions is much higher. A car is fixed to roads and has a map. Mario might know where everything is, but knowing what to do is much more difficult.