Why is SC2 considered the apex of the series? What was wrong with SC1? The whole Yoda/Darth Vader nonsense was predicted by having Spawn and Link playable in SC2, anyway.
It's an honest question, though - it's really hard for me to judge really important things like gameplay balance across the series when I've spent so much time with the first. For example, they nerfed Mitsurugi's air-juggle combo starter in SC2, and while the game felt nearly identical in many other respects, that single move was a staple of my entire SC1 strategy. It may have been an incremental improvement, but for me, it made my favorite character a little less fun to play.