I have a hard time taking people that say that ME3 in general was a bad game seriously to be honest.
Forget its horrible ending for a sec , i can't think of a single main mission that was badly written or wasn't fun.
Mars mission
Getting Eve out of Surkesh.
Tunchanka - getting shot at by a reaper then watch a tresher maw destroy the reaper and mordin dying as he cures the genophage
Rannoch - choosing between quarians and geth or uniting them
Citadel mission - killing Udina and thane dying in heroic fashion
Thessia - hearing the Asaries get annihilated by the reapers on comm while you simply cannot do anything to help them
These are just a few but very emotional moments of ME3 and there are more , so yes saying ME3 is bad is just not knowing what you are talking about , the ending DOES suck but the game in general is great.