I actually enjoy MP2 more than the 3rd. I feel like the 3rd is too segmented (flying between the planets, GUH.) One of the simple joys of Metroid games to me is discovering the hidden connections of all the areas in the world... but there's none of that in the 3rd prime.
The end game fetch quest at MP2 I found to be quite easy actually. I noticed that there were just plain dead end rooms in the dark world the entire time I was playing, and when it came time to find all the keys or whatever, I just made my way to every dead end dark room to find them. Also, doesn't the game give you riddles where the solution is the name of the room you can find the key in? That filled in the rest of the blanks, if I recall correctly!
Have fun at PAX!

Well the clues, like MP1, only reveal in an odd pattern based on the ones you already had I think, and MP2's world is annoying to go through (while MP1's is amazingly fun to explore). I really hated MP2's "temple*" design, and I don't care much for MP3's linear, segmented feel either. But as a game, MP3 was way more fun. It's less "metroid" than it's predecessors, but it doesn't mean it's less of a game.
*i mean like, you'd clear a temple, beat a boss, and move on to the next. There were one or 2 odd powerups where you had to venture out to get, but it was completely unintuitive when you had to backtrack and when you had to keep exploring the same area, and in essence it did segment the game a lot