I would love to provide my input. Hmm... Let's see...
1. Halo Reach
2. Darksiders (X360 and now PC)
3. Mass Effect 2 (PC)
4. Heavy Rain
5. Alan Wake
I gave the edge to Heavy Rain over Alan Wake because I felt more involved in the story in Heavy Rain and there's a greater replay value to it than Alan Wake. I'd tie them if that were allowed and put God of War 3 at 5th. Really though that list is full of disappointment as I've written before.
EDIT: My list is subject to change when I get my hands on Kirby Epic Yarn, GT5 and possibly Metroid: Other M. No Fable 3 and AC: B for me this year