It's important to like how your dog looks. You'll not be fully satisfied with it if you can't stand to look at it. But there's a line you shouldn't cross.
Quite a few lines.
You might like how American Pit Bull Terriers look, but are after a dog that would play well with stranger dogs in the park. Getting a APBT with the intent of trying to train out it's genetic traits (which, I'm pretty sure, are being bred out of it slowly) to be the dog you want is irresponsible and an accident waiting to happen. Just like getting a Jack Russell Terrier because you like how it looks, but expecting it to live happily with Guinea Pigs, or getting a Doberman because of how it looks and expecting it to be welcoming adn outwardly friendly to all strangers.
And then there's the line that covers health vs. looks. You like the look of a Cavalier King Charles Spaniel, but you know for a fact that there is Syringomyelia in the dogs line. You get the dog anyway, listening to the bullsh*tting breeder who insists her dogs aren't affected like everyone elses, just because it's cute.
Or you see the German Shepherds at Crufts, standing so 'nicely' with their sloped, roach-backs and decide to get one because it looks nice, without taking into account the hip problems and the rear-leg weakness the dog can experience because of it's deformed, warped spine.
I can't understand why people have such a hard time walking away from a dog they find cute that has a health record/temperament that wouldn't fit in with your wants. Simply say no, and find a different dog, of a different breed, or from a different breeder, with a more suiting temperament, or a more suiting health record.
We all need to remember that one of the most, if not *the most*, respected show sports out there focuses solely on looks and shoves health and temperament to the side. So long as the dog stands still and lets the judge prod at it, it doesn't even need to lift it's hind legs off the floor properly (going back to the roach back German Shepherd again) in order to qualify and be branded as breeding quality, given a Champion Title and then set out to create more puppies with a similar standard.
I find absolutely NO quality in dogs that champion in conformation. I want my dog to be able to walk comfortably and be able to do the job it was bred for. I want it to be healthy. If that means I go to the breeder that breeds for pet quality rather than the breeder with dogs with slanted backs but Champion titles (despite the fact there's no way in the world the dog would be able to scale a fence or have enough leg power to keep itself rooted to the ground while bringing down a criminal, or have enough agility to herd livestock) then so be it. I'll go for the healthy dogs rather than the wealthy dogs.
To actually answer your question, "cute" came before health and happiness whenever it was Paris Hilton got her first handbag dog.