I played Prime 3, then kind of gave up near the end. Apparently I'd used the generic Energy Cells in the wrong order, now I'd have to go through an entire massive fetch quest to find the last one.
"So, we got into the enemy satellite and now we need ACCESS CODES to use it!?"
There was a fetch quest in Metroid Prime 1 but the rest of the game being brilliant pushed you to go through the trouble of finding all those dumb things no problem. In prime 3 it was just more annoyance at that point. Energy cells, well great, I bet the federation could make some for you or something instead of making you run all over the place.
Speaking of which, the glamor of the prime series began to fade from game to game the less you felt isolated. In prime 2, federation folk were around, sort of, and you had an alien dude that pointed you in whatever direction he wanted you to murder and it was kind of less captivating. Prime 3 simply reminded me of Halo. You had complete contact with the federation all the time, and it just completely bashed that great claustrophobic feeling you'd get in the other games.
