Prime 2 is the best of the Prime series. It had the most creative level design, creatures, and overall art style. Prime trumps Echoes only in story imo.
Now that ive got that out of my system, i dont know how i feel about M:OM. It has automatic aiming in 3rd person mode, so there will need to be some VERY interesting and creative bosses and enemies to make the game challenging or at least retain the "shooter" part of past Metroids.
The 1st person mode seems half assed. There doesnt seem to be much use for it. Sure you can shoot stuff, but without mobility, exploring will be very tedious. Im hoping to be blown away, but i honestly dont know what to expect from this. Digital controls work only so well in a 3D envorinment.