Dogs!
They genuinely love you and give you affection. They know when you're upset and come to you and try and comfort you, when you're excited and happy they get excited with you. Yes they take more looking after than cats, you gotta bath them, walk them etc. Vets bills are higher generally, but the friendship and loyalty you get in return is worth it. Any dog friend will guard you - a large dog, mastiff, alsation etc is usually enough to put would be muggers, burglars off and a small dog, westie, yorkie etc are very good 'alarm' dogs, with my westie the only people he would not bark(yap) his head off at until I told him it were ok, were myself and my 2 young children - I live with parents and even they got the barking treatment.
Cats are ok, but they only show affection when they want something, not just for the sake of it. They're very independant and not very playful. I can see why some would prefer, but for me, doggys win, I prefer my dog friend to human friends.
Sadly my westie Alfie passed away last october, me and my eldest were(still are) gutted. But, we've decided to get a puppy next spring when we've fully grieved, my son has insisted it HAS to be a westie, HAS to be a boy and HAS to be called Alfie. Hopefully Alfie 1 will take it as an honour of how loved he was.