Something new to discuss, eh? Well, there is this one statement I've made a few pages back.
To me, something that is interesting is something that can bring a certain characteristic on the roster that has not been explored yet.
This statement regards to something that can be distinctive, something that can stand out in it's own way. Whether it's cosmetics or capabilities, the character in question has to be something interesting that can grab peoples attention. If the character lacks ether distinction, there's not going to be much to talk about. As Sakurai himself puts it, a character "that would make people play the game".
However, let's just say whatever character that falls into the distinctive pile varies between people. For me the idea of an distinctive character is something fresh that hasn't been explored yet. Like for example, Dillon. Dillon is a character that brings out vibes of the wild west from the 1800's, with both the character and the surrounding universe borrowing heavily from it. The character also has a fairly distinctive fighting style involving using a combination of claws and rolling, which in a setting like Super Smash Bros. could lead to the probabilities of an effective move set.