Original-9.3
It was amazing for a very,very low-budget game. It's good but not the best of the three.
Melee-9.8
An almost perfect game. It added many new gameplay modes, much better and complex yet simple fighting, twice as many characters, and event matches which kept thing entertaining since it's nearly impossible to beat all of them.
Brawl- 9.5
A very good game over all. The subspace emissary was great with it's scroll by action that took hours to beat. Lots of fun bosses. an improved version of break the targets. New characters that are just plain awsome. And 128 challenges waiting to be beaten, as well as a stage creator and tons of new fun levels. So why did it get a lower score than melee? First of all there's no added special brawl features, online mode sucks, not much was changed to the fighting except mainly for the smashball. Plus Final Smashes are very unbalanced, and level creator is very limited.
These are my scores and my reasons.