willing to bet 90% of the people mocking halo reach haven't played through the ending. Number 2 maybe it isn't but it had a brilliant ending for fans of the ip. Though it does lose some points for making you super macho at the end and beating up a bunch of elites while dieing...
It is definitely a less shocking choice then having Ocarina of Time at 3, Pokemon black and white at 12, any call of duties being on the list, or any of the no story mario and sonic games in the list at all, and this coming from a huge platforming fan. This is about best endings, not best game, or even best story.