Sackboy is a great little character and to me LittleBigPlanet was one of the best games to come out last generation.

Sackboy not being Sony's mascot? These guys may know.

Anything that looks like a big turd doesn't do well.

bad user interface ( too complicated for kids) and too much floating!

There is no hate here, just stating facts as to why Sackboy hasn't reached the popularity of popular characters like Mario (Ninty), Sonic (Sega) or even 'Chief (MS).  I'm studying character design myself, and when I look at Sackboy all I see is brown wool eyes buttons threads.  Clearly he is designed to be the all-around-toy, the toy that could be any toy.  Hence he is very generic and does not own any specific personality.  This is the intention of the designers at media molecule.  They never meant for him to be a "flag ship character" or a "Sony Representative" character, otherwise they would have made him more interesting.

Look at the design of Mario and Link, they have highly saturated colors and colors suggest a lot about their character.  By design I don't mean anything stupid like fashion or any bullshit they come up with in Milan.  I'm talking about product and graphics design, like the wheel is designed to roll or the color green is designed to tell drivers that it's okay to Go.  I guess you can say that a solution is DESIGNED to solve a specific problem.  In Sackboy's case the problem was "How do we make this character that people can turn to anything they like?" and Media Molecule devs/artists designed a solution to make his base concept forgettable and he can be anything you want him to be.  The design did not give him any personality because that wasn't part of the problem they were trying to solve, so they removed most identifying marks in him and made his base model very forgettable so that you can "make up any character in your imagination."

Remember I am not attacking Sackboy, he is designed to be as generic as possible so that people can imagine something else in his place.  Had their intention was to create a Mascot for Sony, Sackboy would have been a lot more interesting and possibly have a better name than "Sack" "Boy".  This would be hard to accept as most Little Big Planet fans have a lot of fondness for the games, and so most fans are emotional about this topic.  The road to acceptance is:

1. Denial

2. Anger

3. Bargaining

4. Depression

5. Acceptance

6. ???

7. Profit! $$$

Another fantastic post.  I can't dispute a thing you said.

Sackboy had plenty of potential after the 1st LBP but Sony dropped the ball on the sequel on spinoff, just like always. LBP2 sold 2 million less than the 1st and it was because it looked like the same exact game. People talk about Mario or Zelda being the same but thats just fanboy talk for the most part (NSMBU is a rehash, I liked it but it is). LBP Karting looked like a terrible ripoff of Mario Kart and there you go, already failed franchise. The same exact thing happened with Resistance and to a lesser extent Killzone.

Thanks, this topic has been rattling in some form or another in my mind.

A lack of blocks to break open with his head and magic mushrooms to eat.

What charm and character? He was intentionally a blank slate.
Mario, by contrast, brims with character, from his joyous exclamations as he jumps, flips, and spins, to his endless enthusiasm, to hs childlike exuberance as he run with his arms outstretched pretending to be an aeroplane. He's not just an avatar, he had a distinct personality that it appealing and infectiously upbeat and cheerful.