A great successor and an amazing game in its own right...
Story - 9/10 - Your spaceship gets struck by a lightning bolt and now you have landed on Aether. You find out that the Galactic Federal Troopers are all dead and now you must find and rescue the Luminoth. The story adds much more depth than the original Prime and makes things more interesting. I find that the story does not exactly follow up to the original Prime, but it offers up something new to the action.
Gameplay - 10/10 - The gameplay has not changed since the original, but there has been some minor tweaks. When you start out in the game, you have some items with you. Then, they all get lost except for the Morph Ball. Yeah, you can't lose the Morph Ball in the game. You have to get some of your items back by facing guardians that have these items. Some of the items are still there that were in the original. Gone are the Wave, Ice, and Plasma beams in the game. There are new beams called the Light, Dark, and Annihilator beams which take effect on many enemies throughout the game. There are even charge combos in the game which take massive damage to enemies. Each beam/missile/bomb can open up a different kind of door in the game. Instead of having unlimited ammo, you have limited ammo with the Light and Dark beams. You can get Light/Dark ammunition if you shoot any enemy with a different kind of beam. If you shoot the enemy with the Light beam, you get Dark ammunition. If you shoot the enemy with the Dark beam, you get Light ammunition. There is still the Charge beam, though. The Morph Ball is still there along with the Grapple Beam, Space Jump Boots, Spider Ball, Power Bombs, and the Scan Visor as well. There are two new visors called the Light and Echo visors which are useful in the game. I find the gameplay challenging and much longer than the first one. Basically, there are more Morph Ball puzzles in the game to make the gameplay even harder. The backtracking in the game is still there, but it doesn't mean that it's a bad thing. You'll have to backtrack to every place once you find a new item. It's not a huge impact, really. Metroid Prime 2: Echoes is a fun experience. It will not frustrate you.
Graphics - 8/10 - Well.....the graphics in this game changed a bit. There are new areas that have shiny environments in the game that aren't too blurry. Yeah, that's pretty much said with the graphics.
Music - 10/10 - Wow! The music in this game has left me yearning for more. There is new techno music in some areas that add up to the game's personality. There is also a new Super Metroid remix in the game that is from the Brinstar/Maridia area that is also cool. The music is definitely addicting to hear, especially in the boss battles. Hats off for making great music, Retro.
Replay Value - 9/10 - You will be playing this game again after you have finished it. If you want to get 100% in the game, you have to scan and collect every item as possible. The game is about +15 hours long and it is addicting once you get into it.
Multiplayer - 8/10 - This is probably the game's weakest point. The multiplayer can let you have up to four players as possible. Even though it's the Gamecube, there is no online play or LAN support as you expected. You can play in a team deathmatch and other kinds of modes as well.
Overall - 9/10 - This will be a great game to add to your collection. You won't be disappointed by the fact Retro has done a great job with it. There is still the Image Gallery with new pictures in the game. There is also a Hard mode for making the game even tougher. If there was a third sequel, it will have you leaving high expectations of what it will be like. Nintendo and Retro has done a good job.