R.J.
One that suits your lifestyle and climate.
What's the weather like where you're at?
Don't want to buy a snow dog if it's warm most of the year or they'll be miserable, and you'll be hip deep in fur (huskies, malamutes, etc.). Don't want to buy a dog bred for 100+ degree weather if you're in the -15 to 80 range.
How much space do you have?
Don't want to buy a guard dog if you're super active people. Guard dogs want smallish spaces and are fairly sedentary (chows and pugs and chihuahuas, for example). Don't want to buy a working dog (herders, retreivers, etc.) if you're sedentary people. Don't want to buy a giant breed if you're in a small house or apt (Danes, Mastiffs, etc.). Don't want to buy a toy breed if you're on acreage. Don't want to buy a herder if they're going to be home alone without "things" to herd and courses to run, or they go neurotic.
How much time/money do you have? The smarter the dog, the longer the training period is. W-Hybrids, Huskies, German Shepards, etc. typically take 2 years to train, becuase these are VERY smart dogs. It's like raising a child. Many of these dogs The goofier a dog is the easier they are to train. Many in just a month or two. (Retrievers are the 'Life is Like a Box of Chocolates... never know what you're going to get!" breed. Some are wicked smart and take ages, others are loveable goofballs who take next to no time at all).
The questions go on and on.And the answer of 'best dog for a family' will change with your answers