Metroid has always been my favourite Nintendo franchise and Fusion is one of the absolute best in the series. The GBA is a perfect platform for a 2D Metroid game, with some really impressive sprites and animations, haunting ambient music and really satisfying controls. It's very linear, which can be seen as a negative for a Metroid game, but what it loses there it more than makes up for with its pacing and atmosphere. This is the closest Metroid has gotten to pure horror and I don't know if it would have been as effective with full exploration. The linear nature allows the developers to properly pace your journey and create a much more palpable level of tension. I also think because of this more guided approach it would make a great introduction for newcomers. I honestly think this should be held in the same regard as Super Metroid and Metroid Prime, it's my favourite game on the GBA and one of my favourite games of all time.