Most improved sequels

[Veknoid_Outcast]

Player2 said:

Street Fighter - Street Fighter II

Super Mario Bros 2 - Super Mario Bros 3

Metroid II - Super Metroid

Soul Blade - Soul Calibur

Resident Evil Zero - Resident Evil 4

Pokemon RBY - Pokemon GSC

Final Fantasy VIII - Final Fantasy IX

Suikoden - Suikoden II

AD&D Tower of Doom - AD&D Shadow Over Mystara

Oh, I feel so stupid for forgetting Street Fighter.

I have to change my answer. The gap between Street Fighter and Street Fighter II is enormous, much bigger than that between Super Smash Bros. and Super Smash Bros. Melee.

Good call, Player2.