Would almost agree with this. Metroid Prime 3 is the only one I played on easy, only one I finished exactly once, and the only one I had to repeatedly rest because my wrist was tired. When Metroid Prime came out, the biggest concern was it'd be a FPS and not a FPA or exploration game. So, of course, the second they get the chance, they make the game a FPS.
Having said that, going back and playing Metroid Prime and Prime 2 with the wiimote/nunchuk isn't bad. Clearly it's something that takes quite a lot to get used to though. There's also at least a few places in Prime 3 where it doesn't feel like a bad thing that they used a wiimote. But it suffers the same problem Halo 1 does (haven't played any other Halo to compare): it's basically a necessity to nerf either the enemies or the targeting to compensate compared to keyboard+mouse. That rather ruins it for me from that perspective. Thankfully, it didn't seem *that* bad in Metroid Prime 3. *shrug*