Why? Besides the ambiguity to blue and green endings (assuming you don't have the Extended Cut, which you should have), they were good endings. If you have Extended Cut, you've got a great ending. Or did you somehow expect it to be different?
Technically speaking, Shepard would've somewhat survive through the Shepard VI. Since Synthesis requires Shepard to sacrifice himself to infuse his very essence into everyone and everything in the galaxy, it's highly probable that the Shepard VI would've become fully sentient with Shepard's persona, therefore allowing Shepard to survive in that form.
You were specifically warned about the fact that you'd have to sacrifice yourself. I understand the information was pretty sparse before you actually chose, and the ramifications were only really explained afterwards. I actually liked that. I thought it was humbling to still be part of something bigger than I could possibly understand, even after becoming possibly the most important human to ever live. It's probably for the best my Shep died after Destroy. He never would have forgiven himself for EDI and the Geth's deaths. He was only human, and made a mistake, too intimidated by the idea of taking the kind of power that Control provided, or changing the existence of every living sentient. Anyway, why would you want Shep to live through all that? I thought death was a fitting end for him/her. The ony way the Commander would ever stop fighting, the only way Shepard's story could end.