I'm not sure how Bioware managed to get everything right only to screw it up in the last moments of the game. If this is Shepard's last story, how could players be treated to endings with no closure, and which two of them are essentially the same? I also don't understand how Bioware can't see how this would be upsetting to fans of the franchise. Bioware writers are incredibly gifted at writing characters that make you believe in them, that reflect all that's wonderful and all that's awful about life. The writers make the characters matter to us. So after executing a literary coup that leaves our hearts firmly in their grasp, they seem oblivious to the fact that it HURTS when they rip those hearts out by the roots.
ME3's larger scope means that Shepard's decisions grow more painful and harder to arrive at than in the previous games; and the effects on Shepard's character are more pronounced as the game goes on. As the countdown to the final climax comes, Shepard's outlook gets grimmer, and lonely. This is one time the Commander needs someone to lean on and there is no respite to be found. I don't believe that life is sunshine and unicorns, but many of us play these games to immerse ourselves in a life that's different than our own, maybe even better in some ways.
Is hope that detrimental to a storyline?
Here is my personal wish for Shepard:
Shepard, if he/she survived the events of ME3, retires, and undergoes therapy to help with the PTSD he/she is suffering from, and the survivor guilt. Shepard marries their love interest, has a beautiful honeymoon, and a kid. This makes Shepard think of the boy that died back on Earth. Shepard doesn't retire completely from the alliance, but serves in a consultant role. However, the years and tragedies have taken their toll and Shepard is deeply scarred and broken. After bringing deliverance and salvation for so many, the Commander is grasping for whatever bits of happiness and normalcy he/she can find... Thane once told the Commander that there comes a time when one must rest from war and conflict, that it wasn't Shepard's time, but that it was his. It is finally Shepard's time to rest. The Commander has earned it.