Parents don't need to think twice. Nintendogs is truly suited for all ages. It might even be a suitable test if your kids ask for a real life pet. Nintendogs will give them at least a glimpse of the kind of responsibility that comes with an animal friend.
Innovation junkies should also be very happy with the game. It makes great use of all the features you bought your DS for and while being hyped beyond belief still has a very quirky, off-beat feel to it. Furthermore it proves to be a perfect recruitment tool for not-yet-gamers.
If you are neither casual nor hardcore, but not gaming at all, you should probably ask yourself why you are reading this anyway. But while you're at it let me tell you that even you will be captivated by Nintendogs's intuitive style.
Should you, on the other hand, consider yourself to be too hardcore, for something as childish as a puppy sim you should better stay away from the game. Because before you know it even you will be turned into a wide-eyed puppy lover whose sole and single target in life will be the well-being of his scotch-terrier "Master Chief". You'll eventually be kicked out of your clan because you missed all the important raids last month while training for the next agility competition.
Deaf and Hard of Hearing players will unfortunately have a hard time with some aspects of the game, namely the obedience section which requires players to give orders and pronounce them the exact same way every time.