They went downhill every single moment after the "You exist because we allow it, and you will end because we demand it". Everything they did from that point on was a letdown to me.I loved the reapers Just pissed we never got that final confrontation with that a$$hole Harbinger... Should have had a boss fight in the last one.
Why did they suck to you?!? Was it the writing?! Blame Casey Hudson!!!
They were basically godlike, but the more and more you learn they turn into manipulators and simply more advanced than everyone else. Even Saren - he was at his best when he was maniacally TERRIFIED of the Reapers, not 'indoctrinated' and turned into a cyborg.
Everything people feel and know about the reapers is founded upon what they were in Mass Effect 1. They got progressively weaker and more flawed as the series went on. Mass Effect 2's 'collectors' were outright comical to me. I played the game because I loved the universe, and the idea behind abductions was cool, but look at what it turned into. It was stupid. Harbinger was a clown - and the whole 'genetic material of humans is what we need to make our motivations make sense' is a perfect example of how the Reapers were ruined. You don't NEED to explain everything, and if you do, don't ever weaken your story by your explanation.