• they naturally shy water, so their sense for cleanliness is at best weird (besides, I've seen really dirty cats, especially male, after hunting down female cats across several rooftops - compare this to dogs, all of which enjoy bathing, at least all I've known so far)
• they don't really attach to one master - some furniture or any any stranger is just as good for petting as is the master
• they don't really care where food comes from (or whatever else they might need) (whereas some dog breeds never attach to more than one master, for life)
• they never listen to anything else than their stupid selfish instincts, cand cannot be trained not to eat from the table (whereas a really smart dog learns all by himself to understand what his master wants from him, eventually)
• they are completely insensitive to their master's mood - a cat will come to be petted even when you're as down as possible (instead of coming to lick your face, like a dog would do)
• have you ever seen cats mating? The female cat entices the males like a whore, but what comes next looks a lot like rape to me (dogs are a lot more straightforward: a little sniffing, then go for it)
• what about the noises they make during mating season? (dogs mate silently)
• finally, the simple fact of being a cat is a defect in itself (and not a dog)

To be honest, there are two sorts of big wild cats I really like: the cheetah and the lynx. None of them has anything in common with tamed cats. The lynx even likes to fish, probably the cheetah would do so too, if it had any water for fishing available. There are even known cases of lynxes partnering with hunters for hunt - but such a partnership needs many years to form.

And now one of the best pieces of experimental evidence (that I'm aware of) that cats are extremely stupid:

A friend's friend seven months or so old male cat was sun-bathing on the balcony at the 7th floor (that's more than 20m altitude). It noticed some birds flying around in the trees below, around the 3rd floor (more than 15m below the 7th floor). So it jumped at them. It landed on the pavement below, broke his jaw and some bones in the hip region. Got expensive and sophisticated medical care, had some titanium rods in his bones for a while, and slowly got close to perfectly healthy again. No longer than two weeks after getting rid of the last titanium rod, before all stitches were completely healed, he was acting like crazy behind the net his masters had mounted on the balcony to prevent the same accident happening a second time. In spite of the net, a few weeks later they left him home alone, went for a walk, and found him in front of the door when they came back - he probably discovered a way of getting through the net again, but probably crashed on some tree branches before landing on the pavement this time.

If this isn't monumentally stupid, what is?