A charming virtual child's toybox. Some of the toys are broken and fragile so they can snap easily, please don't push them too far.

While the broken state of this game is something you have to deal with when discussing it, I'm on the camp that thinks Sonic Adventure is magical when it all works. It's just that it's easy for the ilusion to break.
Y'know when you were a kid and one of your figures broke like, a leg or something so you got your dad to duct tape it back? Now whenever you played with it, it kinda looked out of place, and you had to be careful because the leg could detach itself again and all that? But when it the first shock wore out you didn't really care? Yeah, Sonic Adventure is kinda like that.

Which isn't really a great endorsement, no one buys pre-damaged toys. But I just liked the feeling of carefully playing with a broken thing, after a while it just became natural and I could enjoy the great things this game has to offer like the crazy bonkers levels, varied playstyles, godly soundtrack and surprisingly interesting story structure.

I think this can only work because Sonic Adventure's heart is pure, like a child's. A game so broken can only be loved because it's so devoid of cynicism and is so earnest inside.
I'm not sure many adults can get much out of this game, when it was released and nowadays. But I'm sure the kids loved it.