Underrated tbh. Really is just Sonic's version of Mario Galaxy.
Is it nearly as good as Mario Galaxy? Heck no.
But honestly, I had a decent time with this game.

This game is just bad. Nothing else to say really.

What a weird Fisher-Price crossover.

The graphics engine, music quality, and animation are absolutely fine. Sometimes, great! The main issues just boil down to a few points: A lot of the levels are really lame Super Mario Galaxy clones, the writing sounds like it was made for preschoolers and made me cringe hard at it most of the time, and literally all of the new characters and enemies have this "baby's first animal toy set" type of design & I REALLY hate it. The characters all act so 1 dimensional in this game, down to exactly what those "googoogaga" characters are designed to look like as a stereotype in cartoons. And why do all of the enemies have such Disney Jr. faces and huge eyes? Ew.

However, this game's not all that bad, as I was able to enjoy how Eggman was handled and the weird conflict between Eggman and Tails for a while. Eggman was the only character that even had the concept of depth in this game & it shows. I also have to note that a few levels are pretty good, namely ones like Lava Mountain Zone 2 and the Wii U DLC levels (Yoshi's Island Zone & The Legend of Zelda Zone).

I wouldn't recommend buying this over 90% of Sonic games out there, but I would 100% recommend at least trying out a couple of levels if you bought that Sonic the Hedgehog: Ultimate Bundle on Steam and have the Wii U DLC restoration mod.