This is a nitpick. Let's get that straight. Heavy Rain is an excellent game and everyone should play it.
After all, to really bitch about a game, you have to love it first.
So with that in mind, here is the thing: for a mystery game, Heavy Rain is awful light on the mystery.
I don't mean the big mystery, of course. The game wants you to wonder who the Origami Killer is, and you do wonder, despite the obvious freaking clues pointing at him with giant metaphorical neon arrows, mostly because the game actively doesn't just mislead you but rather actively lies about key events.
But it is a big mystery. It's a mystery that gets introduced about five scenes in and isn't resolved until the final act. Everything in between involves gathering clues, and talking to suspects, and (in the case of journalist Madison) being threatened with rape on three separate occasions. There's car chases and fistfights and a nasty bit of business involving a choice of surgical implements, but you don't resolve that central mystery, or even any subset of it, until right at the end, even on a perfect playthrough.
So what's keeping the player going? Where's the payoff? Scene after scene goes by with no questions answered. I can only speak for myself, but I found it exhausting. After you quicktime your way through your third desperate knife battle in as many conversations, and find yourself still with no new information, you're a long way from being in the coveted "just one more level" zone of addictive play.
So this is what I mean when I say it sucks at the mystery. It needs little questions. It needs little answers. It needs them scattered up and down the spine of the game, because if your gameplay is narrative then you need to offer narrative rewards.
And the questions are there. What's the deal with the cop's addictions? I don't know. The game doesn't explain. Why can't Madison sleep? What's the significance of the killer's poem? Heavy Rain throws these issues out there, and even has them drive plot points, but then seems to forget about them, or at least think that explanations aren't necessary. Properly handled, these could have given the game the sense of structure that occasionally feels missing. They could at least have turned the grim march towards the endgame into something that felt less like a joyless descent into failure.
Heavy Rain is a huge improvement on Fahrenheit, the last game from David Cage and his team at Quantic Dream. But it's still got a way to go in learning to tell a satisfying story. I'm looking forward to their next attempt. Will they continue to improve? Really, that's the mystery that's keeping me engaged here.