I'd place it around the start of ME2.
In contrast, ME1's ending may have well been a master class in game cinematography and writing.
The combat wasn't very engaging either it was a boring feeling cover shooter. None of your character abilities or gear or anything seemed to have much of an effect.
Edit: Deus Ex series too
My point was that ME3 was doomed because ME2 utterly failed at bridging the gap between the strong start of an epic that was ME1 and what should have been the conclusion in ME3.
In fact 'fail' may be generous. I don't think it even 'tried'.