apart from the fact that they're loving and loyal and all that sappy shit, :

-they can give themselves blowjobs.
-they can sleep wherever the fuck they want,and as often as they want.
-they have incredible homing instincts : our granny's house is a mile away from our house, and yet despite the fact our dog was only ever brought there in the car, he is somehow able to find the house on foot.
-can you imagine bringing a cat for a walk or playing football with it? or a lion, for that matter?
-they're funny as fuck. just watch them.
-they somehow know exactly what you're talking about. for example, if i tell my mother i'm thinking of taking the dog for a walk, his tail immediately starts wagging
-they can be trained to help the blind, fight crime, and track down evil druggie people! what more do you want?