The more the marrier. 6.5 years ago we looked for 5 or more acres.
Last house was on .11 acres with neighbors 8 ft on each side and house before that was on .09 acres with houses 10 ft on each side. Closest house to us is 89 yards and the other house is 148 yards.
I would not have compained though if I had 1200 acres or more, but property taxes and insurance starts to take it's toll after a few years.