the ending was really ... nothing, echoing most of the main quest. Specifically I didn't like the binary choice* and I certinally didn't like all the stuff about "this is what you left behind". What I do absolutely like is how a new game is presented as a new (parallel) universe, which is nice, but what I would have done is make all the main NPC's slightly different, randomly. Like the Constellation people. Randomize the colours of their clothes, and slightly randomize their features. Just enough that they'll look different, but not too different.
It's also yet another example of how hard it is to make grand stories, but it's also sort of a good example of a Grand Story. It's a Grand Story, but it's also not, because while it is about big multi-dimensional stuff it's also NOT about the fate of those dimensions. You do make some decisions that will affect people, but the story itself is not about THE FATE OF REALITY™**. It's fundementally about you and what you want to do. Which I sort of like, but it also doesn't really work IMO. I have no idea what the good version of this looks like.
*it was the only way to end though I reckon.
**looking at you, Starcraft, the moment the Protoss got involved in the campaigns it went downhill IMO, I much rather play as salty SCV's and marines trying to survive (or Zergs trying to eat salty SCVs and marines!) than Ancient Noble Aliens Saving the Universe™.