On a gameplay level, Nintendogs is limited. The voice recognition system, a vital part of the game, sometimes worked, other times didn't. Also, there should have been more activities for you and your dogs to do. There should have been an expanded dog show section where your dedication to your puppy would be rewarded. The interaction between puppies and other owners should have been better. What is there is good but very basic. The experience needed to be more rewarding than just meeting in a park and watch the puppies play.
On an emotional level, though, Nintendogs is a roaring success. All of us pet owners know that sometimes pets go from being another thing to feed to being vital in our human development. In other words, we create a special bond with them. Even when they can't talk we understand their feelings and the love grows stronger. Nintendogs did this really well. Its the closest thing ever to owning an actual puppy.
Finally, and what I think people are seriously overlooking here, is that the game played a major role in the development of the DS, and helped it evolve from a gimmicky handheld to a serious competitor. Before Nintendogs was released most of the games were GBA ports with tacked-on touch controls, used the buttons and D-pad or were mini game collections. While the voice recognition was far from perfect the touch screens were remarkable. It added a lot to the gameplay and to the emotional value of the puppies as you could touch them, and they would interact with you (by giving you their paw or biting you when you were a jerk).
Without the success of Nintendogs perhaps there wouldn't be games like Ninja Gaiden DS, Starfox Command and Phantom Hourglass in which touch screen controls are taken to a whole new level. And there wouldn't be games like Brain Age and Professor Layton, games that transcend age, stereotypes, cliches and social mores.
Speaking of which, I am getting very tired of hearing angry editors and fans rag on the Wii and DS for attracting a new set of gamers (OMG old people play Wii LAWL!). For years videogames have always been seen as child's play, stuff that doesn't add to the welfare of society, or are accused of being murder simulators. The Wii and DS are slowly but surely breaking that wall away and allowing games to be social activities we can all enjoy instead of a stereotyped niche. Which would you rather hear...
"The Wii is helping people overcome injuries through unique therapies"
"The DS and Brain Age is helping people become well aware of their intelligence"
'The Wii is helping senior citizens have fun in their golden years"
or...
"Videogames are for losers"
"Murderer was inspired by popular videogames"
"Videogames are murder simulators?"
I may have gone on a tangent here, but Nintendogs is a fine example of games that think outside the box.
So to end this, Nintendogs may or may not be everyone's favorite game but to deny its impact and success not just on the DS but on the entire gaming industry is being foolish and ignorant, fueling the stereotypes that are already plaguing our favorite hobby.