I've only ever played the Metroid Prime 1-3 (yeah, yeah, not playing a 2D Metroid crosses the Moral Event Horizon, I know.). Sadly, I was too young and unskilled to finish Primes 1 and 2 (I really should get on that, in retrospect.) However, I did finish Prime 3, and what I did play of the Prime games was some of the best gameplay I have found in a long time. The massive ammounts of information you could peice together with the scan visor, or just ignore if you didn't care made it awesome.
That said, I don't have high hopes for Other M. It seems to be a major downstep graphically from Corruption, and while graphics do not make a game, I don't like seeing a series backpedel in any area. Furthermore, it just looks to be all action and no story. While the early Metroid games were able to pull off minimal story (or so I am told) the Prime series has left me craving for a game where your scans reveal details as Samus would recognize them, and leaving the player to peice together events and implications. That alone was a large selling factor for me, after I saw only a small part of what Prime did with it. I recall in Echoes
going through the space pirate encampment on Light Aether and seeing their normal rambling about Samus as "The Hunter" when I noticed some of the logs said "Dark Hunter" instead. When I came across one that had a pirate losing his mind over both The Hunter and The Dark Hunter going after them, I was able to know for sure somthing was up...only to be dropped into the first fight with Dark Samus.
I just don't get the feeling Other M will have experiances like that.