Well, I'm not quite sure. The story follows a 10-year-old boy collecting cute monsters to battle against other kids. I don't there's a single Pokémon that would be considered scary. Even Mewtwo is cute.
The gameplay itself is not aimed towards little kids. I've mentioned many times the mathematical equations that goes into creating the perfect team. It's pretty easy to beat the game but if you ever want to compete against others then you need one hell of a good team with plenty of time and research.
In the game both kids and adults battle with Pokémon. Though with G/S/C you had these crazy adult nuts called PokéFans. A grown man wearing a pikachu shirt and hat with his gut hanging out. Ugh.
I've witnessed man in business suits playing Pokémon on the train you obviously it's a game that can be enjoyed by all.
I do with the appearence of some monsters weren't so cutesy. Look at some Digimon for example:
http://www.geocities.co.jp/AnimeComi...mon/st-517.jpg
http://www.geocities.co.jp/AnimeComi...mon/st-567.jpg
http://www.geocities.co.jp/AnimeComi...mon/st-494.jpg
http://www.geocities.co.jp/Playtown-...mon/bo-480.jpg
http://www.geocities.co.jp/Playtown-...mon/bo-456.jpg
Digimon has a mix of cut and scary monsters. They for the most part start off cute and then as they grow and evolve they become more monster looking and intimidating. This is what I think Pokémon should do.