The writing in ME2 and ME3 wasn't that bad, but they sure as hell stopped feeling like role-playing games. If BioWare had more time then maybe we would have had three different endings.
Ending 1: Crucible is a superweapon, blows Reapers all to hell, good guys win.
Ending 2: Crucible doesn't activate, Harbinger harvests Shepard, you play as Harbinger and help the Reapers win.
Ending 3: Crucible activates, but your war assets aren't high enough to win the war, so nearly everyone dies.