Well, what about the game would end when Admiral HAckett says Crucible don't fire and Shepard doesn't know what to do?
For me it would be another epic ending.
That would be slightly better, but basically leave too much hanging. The central conflict of the entire series being unresolved.
An acceptable ending for me - though I'd still prefer something else - would be, if after dealing with the Illusive man we see Shepard and Anderson bleeding out, watching what's happening outside, just after Shepard managed to activate the Crucible, with only the Reapers being destroyed, not the Mass Relays or the Geth. Though that would still leave plotholes like how they managed to move the Citadel.
Possibly with some Fallout style narration about what happened to your companions and how your actions affected the galaxy following your death. EDIT:
I don't mind, sad, downer. everybody-dies or bittersweet endings. Some of my favourite endings have been those. I have a problem when that ending doesn't flow based on the rest of the story or when it's done to appear grimdark or edgy or for whatever other cheap reason.
If they don't improve I'm just going to consider Shepard dead at the end of ME1 - the cutscene sort of set that up at the start anyway - having saved the galaxy, with the Reapers safely asleep or locked out of the galaxy.