It really depends on your family, where you live, how big your house is, and a few other factors such as your level of income, how old your family members are, and how much you and the rest of your family are emotionally invested in the idea of taking care of a dog. Kids will beg and plead for a pet puppy, but then get bored of it after 2 or 3 weeks, and suddenly its now mommy/daddy's new puppy... and if mommy and daddy are too busy to raise the dog properly, you are essentially dooming the dog to a less than ideal life, where it isn't exactly wanted, and that is NOT FAIR TO THE DOG because the dog didn't have a choice in the matter!
Also, if you aren't making much money in this down-turned economy, like me, you definitely don't want a dog that inhales food like it is going out of style. For your budget conscious dog owner, go for a small dog, preferably a short-haired mix-breed. They require the least amount of food, bathing, and accessories, and if your dog gets sick, smaller dogs require less medication, which can be veeeeeeeery expensive per milligram.
If you have a family that likes to take care of dogs, and your kids are a little more grown up than toddlers, then I'd recommend a somewhat small mix-breed dog, such as an Australian cattle hound/German shepherd mix. These dogs are very energetic, but they typically don't completely spaz-out like some of the super energetic toy-sized dogs. These dogs are great for playing fetch with and getting you/your kids exercise by walking them a mile or so every day. This dog is big enough to be a good guard dog, but not so big that you have to worry about it literally killing you in your sleep like the bigger huskies and malamutes sometimes can. I really miss my Aussie/German mix, she could play fetch all day long, sprinting back and forth, and she never got tired or bored.
My current dog is a Dauchsund/Chihauhua mix, and she is a completely lover. The friendliest dog I have ever seen, period. My dog has more friends than I do! She isn't exactly a smart dog, I mean she will never bring me my slippers or the newspaper, but she is a loud barker and is a great alternative to a door-bell, because even the slightest sound at the front door will set her off. Plus, she is so small and so lovable, I'd feel perfectly safe leaving her in a crib with a new-born baby and leaving the room, that is how confident I am in her friendliness (not that i'd ever actually leave a newborn baby unattended with a dog).
Choosing a dog is a personal choice over all though, you can follow a million different peoples guidelines on what to expect from a dog, but it really boils down to how the dog was raised, and not so much on the breed of the dog. I have seen vicious pugs, and lovable rottweilers... so that just goes to show you that if you are a good owner, and train your dog well, its hard to have a bad dog!