I have six cats, five of them came from the shelter and one was semi-feral and picked me. My biggest baby, a cat I'm positive never set a paw outside a door, adores hunting and torturing the prey to death. It's impossible to get her trophy from her, she'll eat it first (eating the prey, believe it or not, is not instinctive. The killing bite is, but eating what you've killed is learned). So I came downstairs today and there was a murdered mouse in the middle of the living room floor.
Okay, my $0.02, essentially, cats have retained that self-sufficiency because they have always been solitary. Dogs are pack hunters. Dogs, inherently, need to be in a group structure to function and be happy, which is why they work so well in our households. Essentially, dogs are good soldiers. They are like us, we're pack animals, too. Believe it or not, dog body language translates over easier to humans than cat does.
Cats don't really need us but they like comfort and they are opportunistic. It's a bigger stretch for a cat to "learn" human society because they aren't really wired to operate in a group, so there may always be that element of aloofness that some people find off-putting, it depends on what they learned in the nest from mom and how much exposure to humans they had from the time they were tiny kittens.
Think of it this way, cats don't have the desire to grovel to gain your approval because there is no concept in their mind of moving up in a heirarchy, it's just not there. In a cat's mind, humans are people they live with. Dogs, however, are all over their humans because (ideally) the human is the pack leader and it's beneficial to seek the leaders approval because that will make your life better and move you up in status.
Taken down to it's essence: dogs see us as superior to them, whereas cats, inherently, see us as their (slightly clumsy and retarded) equals.