I still have the first and second one both for gamecube but i play them on my wii, I beaten the first one. Metroid prime was so easy to kill in his second form but his first form was a loving pain because he kept changing colors and would not sit still.
I still yet to beat echoes, I started a new game again to try to get all of the items and scans before i fight emperor ing and forget you dark samus. She made me died a number of times because you have like 8 Min's to beat her before dark aether falls apart on you.
EDIT: My most hated boss in this series is the boost guardian, Took me 2 damn months just to kill it. My only way of killing this guardian was to rape it with the light beam. Only about 5 energy tanks, No safe zones and high damage from the guardian. Lucky the pillars it breaks and the enemy's it summons to assist drop alot of health.