I've played all the Prime games (except Pinball and Federation Force). I've played through Prime 2 two times, once on Gamecube when it came out and once on Wii via the Trilogy. While it was a nice "token" touch, I personally found the Screw Attack stuff to be awkward and forced compared to how it was handled in Other M. Prime 2 did double down on a lot of interesting ideas and mechanics, but the Light/Dark mechanic was way too overbearing (and uninspired) for me. I actually found it overly convoluted by the end. I did like the new suits it afforded Samus, but in terms of areas, I think only the Torvus Bog felt right to me.
Something about Prime 2's overall motif felt...sterile and bland. Prime 3 was too linear at first, but it got better as it went along and had some nice use of the Wiimote. I think I had more fun with it than Prime 2, and it had some interesting puzzles, but I don't remember too much about it. It seemed like it was remixing planet ideas, too, IIRC. I certainly wasn't blown away by it, I know that. I'll probably have to replay the first three again, eventually. What's strange is, while it was limited, I really enjoyed Prime Hunters a good deal--I'm talking the single-player. I felt it used the planet hopping with getting those special keys better in some ways than Prime 3. One thing I do know is I thought the Phazon stuff was overdone, especially by Prime 3. The Dark Samus plot bugged the heck out of me, because we were just coming off the SA-X plot, and to milk that for three games was overkill and uninspired.
Metroid Prime 1 felt the most balanced, but then, I readily admit it relied a lot on Super Metroid. I think the Chozo ruins/jungle and the frozen drifts areas, which were not in Super Metroid in any form, were more exciting than anything new the series did afterward. As for the Spider Ball...it's nice and all, but it's not the Metroid II Spider Ball. It should have been called the Magnetic Ball or something. I don't want another 1st-person-centric Metroid...or, if I have to have one, then I want a game where you can switch between 1st and 3rd person on the fly after that entry in a much more fluid and comprehensive way than what we got in Other M. And to be clear, I'm not saying Prime 2 and/or 3 were bad games, I just felt I'd already gotten enough out of that scan-visor-type FPA formula with Prime 1. Prime 1 was actually set to be 3rd person originally, but the developers had too many troubles dealing with it, so they settled on 1st person. So to me, the work should go on. I mean, we wouldn't want every 3D Zelda to be 1st person, as far as I am aware. (By teasing the elaborate Morph Ball sequences and Screw Attack sections, it's kind of a concession that there is more to be done in the 3rd person.) But I'm pretty sure Metroid Prime 4 is just going to be Metroid Prime, with maybe a bit of the newer Halo games thrown into it. Maybe I'll be surprised.