The problem I see is: Cartoon games often flop. I remember very good games like Beyond Good and Evil (a superior mix of adventure, rps, sneaking, racing and fighting) but it was not the success I expected it to be. The reason might be the cartoon setting.

The same happened with the German RPG Venetica. It is a cartoon game and I remember lots of forum postings where gamers complained about this.

But kids love cartoon. So it just depends on your target audience.