Classically Flowing...
While the notes of this song haven't really been changed, the way it flows is very nice. It isn't super fast, it isn't super slow. The flow of the notes is perfect. It isn't hardcore or epic, but it carries a feeling of moving and continuing onward, almost like a raft flowing down a river, or a car driving down a highway. Metroid was a game where Samus moved on from area to area fighting enemies and trekking through endless corridors. This song fits almost perfectly into that frame of mind when you think about it.
Excellent work my friend. You've captured the ongoing flow of Metroid in a simple and effective song. And its catchy on repeat too!