I really like the graphics style. It's solid and clean, without cluttering the screen or overloading the player with flashy graphics. The thumbnail on the game is what made me click and take a look as well, it's the kind of game I'd have loved as a kid. The title image of all the characters standing at the cliff is cute as well.
On the downside, the UI is so basic that it makes the game seem like there's nothing more to it than avoiding getting hurt. There's only health icons and that's it. Not even an indicator on how many coins you've collected (or am I missing something and the coins and stuff aren't actually used for anything?).
The characters and gameplay look fun. From the video it looks like the controls are really responsive too, which is a plus as there's a lot of 2D sidescrollers that have very 'floaty' controls, which imho really detracts from gameplay.
Unfortunately it's really hard to tell what sets this game apart from other 2D platformers. The video really just shows characters running through levels collectintg what looks like coins. But there's no clear objective, no obvious use for the coins, and (from what I could see) shops or ways to upgrade your character.