We have an almost 1 acre 6 ft privacy fenced yard. =D and Gonzo & Fozzie run around it several times a day, its awesome especially for their zoomies before bedtime. But, Gonzo especially, would not be happy only getting yard exercise every day. He gets 1-2 long walks every day, and they usually go to the dog park or the off-leash park to play frizbee or ball.

I think it does depend on the dog & the owner. You CAN live in an apartment or without a yard and maintain even a high energy dog, but it takes tons & tons of work. I know some one with a happy, high drive Border Collie who lives in an apartment and works. He goes on runs before work and to the fenced park after work, and a dog walker visits him for 30-60 mins in the middle of the day.