I agree with Gempress. I live in a 4 bedroom house with my boyfriend right now, and I can tell you that just cuz it's a beg house, Boone gets little to no exercise in the house, or in the backyard. Really his exercise comes from his walking, or dog park. So I think the size of the house or yard really should be irrelevant when deciding on a breed. Except of course getting a Great Dane in a two room apartment is a little silly. ahah
I love offleash parks. A good hour there, playing with other dogs, and running like the wind is as good as a three hour walk in my opinion.