The Collector's Edition looks so much better.
They could be trying to entice people with almost false marketing. They know that people who bought Mass Effect 1 are likely to buy Mass Effect 2, so they have to widen their pool, and what better way to do that than mislead people into thinking they're buying a Halo/GoW style game? It won't matter to them if people buy it and never oplay it because they will still have all that lovely money, and anyone who buys it for the misleading boxart and likes it is more likely to purchase ME1 and then ME3.
It could be an extremely clever marketing strategy, rather than a generic one.