Yes, cats on average live longer than dogs. Large-breed dogs may live about twelve years; small-breed dogs, about fifteen. Cats will live fifteen to twenty years. Siamese seem to be especially long-lived, with the elders among them living to their mid-twenties.
An outdoor cat lives about five to nine years; a feral, about five years. Indoor cats have the best life expectancy.
There is different information every where you turn on the topic. In general, the larger the dog, the shorter their life span. The giant breeds (like Danes) live roughly 8-10 years, while very small dogs have about the same length as cats.
The average age for cats (again, depending on what you read) is actually about 12-13 years. That being said, there are lots of cats that cross much younger, and many that live into their late teens, and possible early 20's. For all the cats that I've lived with over the years, the 12-13 is very accurate, even though I've lost some in their late teens, and others before they turned 10. My oldest cat was 18 when she crossed and she was feral.
My experience is that cats do live longer than dogs. Our dogs that have been in the 50 pound range typically lived 11-13 years, our smaller dogs have lived 16 years and 10 years.
Our cats have lived much longer lives. We have a 20 1/2 yo, 13, and have had an 18 yo in the past. of course, they are all indoor only.