Metroid Fusion is the 4th Metroid game and has to fill the big footsteps of Super Metroid.
Gameplay: The gameplay is the exact same as in Super Metroid. You play Samus Aran and you're walking through a big space station, kill enemies with different weapons and look for hidden items. The only difference is that you don't have as much freedom as in Super Metroid. You get to 6 different areas but when you arrive in one area there's no way back. You have to stay in the area till you defeat the boss and then you can go back to the former areas to search for items. And as in Super Metroid you can collect many many missile expansions and energy tanks. Also different is the difficulty: Metroid Fusion is easier than its predecessor. The enemies aren't very hard and most of the boss fights are disappointing and way to easy. But in the end the gameplay is still a lot of fun and the game motivates to look for the hidden items.
Story: Metroid Fusion starts up with a lot of story. Samus infects herself with an X-Virus and the only way to keep her alive is to give her Metroid DNA. So she stays alive and goes to a big space station to investigate the X-Virus. On the space station Samus gets help by an AI which leads her through the station and gives her some of her upgrades back. The story has some cool twists and is getting told partly with comic scenes (posted screenshot).
Graphics/Areas: The graphic of Metroid Fusion is fantastic and the areas are just wonderful, creative and beautiful (some of the posted screenshots) and look better than in Super Metroid.
Sound: The sound is good and a big part of the good atmosphere. But as good the sound in Fusion is, it's not as good as in Super Metroid. The atmosphere is still good and something special on GBA but compared to the great sound and atmosphere of Super Metroid it's worse.
Conclusion: Metroid Fusion is a good game with a great gameplay which motivates to discover the world, and very good graphic and beautiful and creative areas mixed with an interesting story. Unfortunately the sound and the atmosphere aren't as good as in its predecessor and the enemies are to easy and most of the boss fights are too simple.