I must say, I never played the original Metroid games (going to get them on VC prior to M:OM) and never cared for the Prime series despite owning Prime and Prime 3. Neither my son nor I could ever get into them. But M:oM really has me excited. I love the quick, fast arcade 2d Metroid style mixed with FPS elements and the cinematic story.
I'm a more casual player, and I find this, to me, looks to be a very fun and accessible game to play. I could see this appealing to a lot of people outside of Metroid fans, if they know of it and if they actually get their hands on it to see how fun and accessible it is.