As for the SSE, I was a bit disappointed in it, it was good, but it was not amazing. Allow myself to elaborate, the SSE is to Kirby Super Star as Super Mario Sunshine is to Super Mario Bros. 3. Both are solid and good games, however, they lack the brilliance and greatness of the other game I mentioned in the comparison. It also does not help that I beaten KSS 100% for the 100th (I did not beat it a 100 times, but obviously I have beaten a lot) time a week prior to playing the SSE.
Most people say the problem with it being too short. However, Super Metroid, Gunstar Heroes, and Sin & Punishment are all really short games that can be beaten in less than two hours, however, they are redeemed by their level design, gameplay, soundtrack (especially in the case of Super Metroid), and boss fights. While, the SSE has good graphics and great cutscenes, I found the gameplay uninspired even for a Kirby-based Smash Bros. platformer.
It is not doubt a massive improvement over Melee's Adventure Mode, however, as a stand alone game, which Sakurai was hyping it up to be, the taste of it is quite flat. There are only a few boss fights (seven), about half of them are forgettable.
The enemy design for many of the enemies are also downright creepy, and most of them look like they were ripped straight from Kingdom Hearts, which is not a good thing. I would have preferred if the enemies were of enemies from Nintendo series, or based off of enemies from Nintendo series. Many of the enemies are also quite frustrating to fight, as opposed to being both fun and a challenge (see the Metroid Prime series on how this is done).
Also, on the subject of enemies, I don't like how I have play "Pokemon" in order to get a trophy of the enemies and bosses in the game. The trophy bases take a couple of second to chuck and most of the time some enemy you already have alway gets hit with it, not to mention the enemy most be nearly dead in order for the trophy base to work. It also does not help that trophy bases materialize very rarily.
As for the level design, it is quite solid, and for people who have not played Sakurai's finer works or the 2-D Marios or the Genesis/Mega Drive Sonics, it should be good enough for them to declare it to be the best 2-D platformer they ever played. However, I find myself hardpressed to remember a stage. The key to many successful platfomers is to have varying gameplay and make as many stages as possible memorable. Unfortunately, in the SSE there were only two or three levels that I could say were memorable, and even then those stages only lasted five minutes at most. Perhaps, I am simply spoiled from having played some of the 2-D platformers ever.
Also, don't get me started on the plot. The plot was obviously the biggest failure of the SSE. Why oh why did they have to hire the plot writer for FFVII and Kingdom Hearts? I bet even Sakurai himself could have written a better plot for the game's Adventure Mode. The SSE is a textbook example on why it is a bad idea to make an "epic" game with solely silent protagonists and antagonists. Sakurai said that character's pasts and personal torments would play an important role in the plot, yet that never happened. Tabuu suffers from Time Devorer Syndrome, which means he an antagonist who does not rear his head until the last hour of gameplay and there is also no explanation or a convoluted one as to why he even shows up (Necron from FFIX and Andross in SFA are also examples of this). Also, I think too much prominence was given to Kirby characters. Although I have not completed the game yet, I have seen the ending, and all I have to say is, what ending?
Right now, I am in the Great Maze, and let me tell you this yet another fine example of bad game design. Revisiting all the levels in a maze-like structure to elongate the length of the game, just reeks of the Triforce Fetch Quest at the end of the Wind Waker, perhaps even worse. Not only that, you need to find and fight almost every character in the game as well as almost every boss with the exception of Master Hand, Crazy Hand, and Tabuu. I don't think the development team thought the final level through, and if there were indeed people thinking that it was a good idea, they should probably be hit over the head with a shovel.
Overall, I give the SSE a 7/10 or maybe even a 7.5/10. It is a solid platforming experience, but by no means comparable with even with weaker Kirby titles such as Kirby's Dream Land 3 (which I in the minority and think is a great title and perhaps a masterpiece).