Starting a new thread full of spoilers, so I can get a little more specific on how I feel about the ending. As I mentioned in the other thread, that whole bit with the Normandy, and who pops out after it crashes, all just feels kind of forced. You can tell it wasn't written by the same team that wrote the wonderful missions on Tuchanka and Rannoch, or even the one's who wrote the London mission, which I was incredibly happy with! I feel like the end would have been 1000 times better had they cut that out entirely, and skipped right to stargazer and his grandson talking about the stars. This was a nice touch, IMO, and I'm glad I stuck around after the credits to see it.
That Normandy scene is really my only gripe about the end as a whole. It seems to me that they should give us full closure, or none at all. Don't just give us 1 little scene that raises more questions than it answers. I would have been totally fine without that scene, and just show us glimpses of your choice's effect on the galaxy as a whole, and leave it at that. Otherwise, they should have gone to the other end of the spectrum, and show us what specifically happens to EVERYONE we care about. I'm talking about a LOTR type ending, where after ther final conflict is resolved, there's still more than an hour of movie left!
I played all 3 endings, out of which the synthesis ending made the most sense to me. At 1st, it sort of bothered me (as it has been well voiced here) that all 3 endings trigger the same cinematic, with a different color fire. After giving it some thought, however, I realized you just have to believe in the narrative. The catalyst explained to you exactly what would happen as a result of all 3 choices. So, if you work it out in your mind, you know what happens eventually, regardless of the cinematic you see. Plus, the kid is an allegory for God, do we really think he will be wrong about what happens next? Then I also realized ME2 ended the exact same way. Destroy the collector base or not, the cinematics were largely the same, but we trust in the narrative that either says "We'll find another way," or "I don't think trusting IM was a good idea."
Lastly, there's the issue of choice. Although the choices you made throughout all 3 games have no impact on the final ending, I don't think that makes them irrelevant. Shephard was destined for this ending. Ever since taking command of the Normandy for the 1st time, we should have seen this coming. Defeating the reapers wasn't enough... Shephard was destined to become a legend by saving not only the galaxy, but saving life itself, FROM itself! I think the Illusive Man was right when he tells you, "This is bigger than you or me or anyone!" And that's what the final choice is, bigger than anything you ever expected. Point is, the decisions you make all decide how you make to journey to reach this destiny. And it's amazing to me that 100 different roads all lead to the same place. I finished the game with my Paragon, and even though I know how it all ends, I'm anxious to get started with my Renegade so I can see just how different his road to end is.
Just my $0.02...