I think the scores are quite fair, actually.
There are perfectly good points given for both games. By no means is either one a bad game, but both have their highlights and their low points. It's all a matter of personal opinion of which categories carry more weight. I usually like my career modes to be somewhat decent at least, and for being a racing game, there had better be some form of multiplayer. For not having an offline multiplayer mode really bothers me, A LOT. These games are meant to have some kind of 2 player interaction at least, and racing against an anonymous player isn't nearly as satisfying as playing with a buddy next to you. Online multiplayer is a luxury feature, but by no means should it replace the default, same system multiplayer.
Besides, comparing the two is quite difficult, if not for the cat that there are different points each one emphasizes on. So comparing each one in stuff like Vehicle variety (The game is called Excite Truck) isn't much of a point. Obviously, Motorstorm is going to trounce Excite Truck in all aspects of graphics, since Excite Truck clearly sacrifices its graphics for some innovation, which wins it some points in the fun factor. At the end of the day, comparing these two games is like comparing apples to oranges.