I love Metroid. Fusion is my favorite gba game. So getting Zero Mission was a no brainer. Heres why I like Zero Mission.
Graphics: Zero Mission looks pretty much the same as Fusion. Zero Mission does have cut-scenes which are nice, but everything else is pretty much the same. Which isn't a bad thing.
Sound: Everything sounds pretty good. You might have to turn down the sound for some of the bosses roars. The music is classic metroid and sounds great.
Gameplay: The controls haven't changed from Fusion. There are a few new devices such as morph ball rails and cannons. These work pretty good. The only real problem with the gameplay is that Zero Mission is just plain too easy and short, and the boss battles are like a joke. The hard mode is a better difficulty, but you have to play through the normal mode to get it.
Replay: Zero Missions replay is a lot better than Fusion because once you beat the game you unlock the original metroid. Plus , just like fusion, Zero mission is just so much fun to play through over and over again.
Overall. I liked Fusion a little bit better than Zero Mission because It had a better difficulty. Even though this does have the original metroid. This is a great game. Don't miss it.