my opinion is that the first was simple but lacking in things to do without a second (or preferably 3 more) player(S). Super smash brothers melee solved that problem completely with such things as all star mode to name one but the characters kind of ran together with clones (link and young link). but the items were vastly improved as well as graphics and game play, but the best additions were the side b as an extra move and the ability to charge your smashes. Then came brawl (after 7 long years). this game was also a vast improvement especially with the graphics and the smoothness of the controls. the sub space emissary was fun but repetitive. The clones were given there own unique moves instead of cloning them again. Online mode finally gave people without friends, or friends that sucked to play this game because of online mode. online was very smooth for the most part and always gave you some way to improve your game play. but the best add on was the ability to make your own stages, which keeps me entertained for a while.also you can turn off the smash ball if you don't like it but i think that it was awesome. some things i didn't like are that the items are not as cool as on ssbm. Also the stages weren't as fun as on ssbm. that being said all were fun in there own unique way and each one improved on the other. (I feel sorry for whoever sat through this whole assessment)
