It's really a matter of opinion and your lifestyle, finding out what kind of dog suits you best. My personal favorite is a German shepherd. They are loyal, loving, playful, protective, and very smart, not to mention beautiful;)
It depends were you live. If you are in a 4th floor tiny apartment in a huge city a hyper dog that needs to run probably isn't the best. Research the different types of dogs on the AKC OR ADBA (American dog breeders association) websites. Those sited will give you a rundown of the different dogs traits, climates that are best for them, health problems that are prominent in the breed, if they need a yard, etc. etc. Good luck
I have the sweetest little dog on earth. He is a Scottish Poodle Terrier, he is as sweet as heaven, never bites, and is pretty much potty trained with the training. I recommend, small lap dogs with kind personalities, but it's all up to you.