^That's debatable. I mean at least it was something new to fight and actually expanded our understanding of the reapers a little (whether that was something worth knowing is neither here nor there.) The ME1 end boss was just a reskinned geth hopper chucked into an enclosed space.
Actually, the human proto-reaper is only a lame boss in retrospect after you've had to fight it a dozen times and finally figured out how to Cain it to death in 30 seconds or less.
The FIRST time I saw it, I shat bricks.