Apparantly they are building an entirely new engine to run this game. Maybe the MGS4 engine really couldn't run on the 360. I really wanted to see another game use it too.

As for this game not being quite the megaton MS hoped for, well its a spin-off that isn't even exclusive which Kojima is barely involved in. I'm still more interested in Rising than Peace Walker though. The idea of a MGS game playing like Ninja Gaiden seems like a dream come true. Plus I'm still a sucker for shiny graphics Peace Walker is definitely on my radar though.