Back in 1987, Konami‘s MSX2 release, The Treasure of Usas, wowed everyone with its ace graphics, colourful sprites and smooth movement. It really showed that the MSX2 was a machine to be reckoned with.
Usas is a weird mix of platform game and RPG, although the role-playing elements are very light. But you can in fact play any one of two different characters (WIT or CLES) and build their vitality, speed and jumping prowess as you go, which is somewhat unique and interesting.
The Treasure of Usas even has pretty decent boss battles (for a platform game), although it is no Super Mario World in that respect.