Haven't even finished part 1 and it feels like I've finished 5 games.

Took me about 35-40 hours to 100% complete (which I think you should do, though the "bad" ending still felt solid). Plot takes a bit to get invested in, but in terms of gameplay, it's all killer and no filler. Insane music, and great visuals-- easily a modern classic. Sabotage Studio does it again, and now I'm convinced they will keep doing it.