The endings were narratively short and explain nothing but I get what they were going for. The real issue is that you basically have to stand on the spot and decide. Should have written the bloody star brat into it earlier so you'd have time while blowing away brutes and watching Garrus get raped by banshees to figure out what you want to do. The quick decision is pretty poor.

Furthermore, I think the true lasting annoyance of this game will be how little the decision making throughout the series truly matters. I did everything the paragon way so everything survived (except me). In the end, I can only think of two decisions that would mess the game up: Killing Wrex (which I have NEVER done and will never do) and saying "naaw, don't want Legion on my team" (which my next character actually did as well as give the base to the Illusive man - hopefully that'll add something). The rest get you similar outcomes regardless. Perhaps if your team doesn't all survive the suicide mission, but really, who wants that? If they don't, Mass Effect 3 isn't nearly as much fun because they'll be less to do. Or they'll put in stand ins (I don't know) and then they'll be no interesting side points.

If you're going to make a true "choose your own adventure" gotta work a bit harder to make things different.