The SSE is one of the most disappointing additions onto Brawl, mainly for the fact that for a fighter such as SSB, a storyline just doesn't go nor is needed other than unlocking characters for multi player.
While I'm glad they didn't make it unbearable like Soul Calibur 2's, it still doesn't meet up to a story line based game, even though Sakurai had the help of the FFVII creator. The plot doesn't make sense in some places, the enemies are very unoriginal, and the style is just like in Melee, only without past Nintendo creatures.
I thought there wasn't anything wrong with the Melee adventure mode, it was a good balance of story and adventure for just a means to get unlockables and coins. I feel this was mostly a waste on programmer's and graphic artist's time that could have been used to perfect the roster, and to declone several of the characters, make things more original, and to add more that the fans have been requesting since the announcement of Brawl. Also, the cut scenes tend to be a bit hefty on disc space.