I've suspected it for a long time; when I was growing up, while I never hated my parents' dogs, I was never particularly inclined to play with them. I thought my neutrality/mild dislike was due to their lack of training (and thus lots of pee stains everywhere). I assumed that my lack of enthusiasm for my sister's pitbull was due to the fact that he's huge and still thinks he's a lapdog. But it wasn't until I had to live with one again when my sister and her fiance adopted one that I could say for sure:
I don't like dogs. Particularly puppies.
I mean, don't get me wrong, this guy is adorable:
But there's a huge difference between seeing he's cute, and actually dealing with him when he finds his way into my laundry and chews through my underwear, starts stealing food off counters and from the trash, tries to hide his poop in corners, and comically misunderstands the cat's warnings as trying to play, terrifying her so much that she can almost never leave my room and has a hard time going to her food.
I much prefer the company of cats, particularly the cat I'm living with. I like coming home to a cat snaking her way through my legs, purring softly, while I make sure she's fed and watered and having her occasionally snuggle up with me while I read or work on the computer (even if sometimes it results in her waking back and forth repeatedly in front of my computer/book/phone as if saying "pay attention to me already!"). I like laughing at her when there's a moth trapped in my room and she dances all over the place trying to catch it, or squishes her head through the blinds to stare at the birds outside and make strange meowing/purring noises at them.
It's a nice relationship - we both give each other some attention but mostly do our own thing. As opposed to dogs, which seem to require much more attention than I really care to give. I don't hate them, and I can put up with them, but I would always choose a cat or no pet at all before I owned a dog.
