What's a good dog-life?

Everyone likes a happy dog and everyone would try to give the dog the most suitable life. I know I do. But what's a good dog life? Sometimes I feel like I don't always give my dog everything he needs, and it makes me feel bad. A dog needs to use its body and mind to be happy, some more than others. Can a dog in a household get a good life? I try to give my dog as much freedom as possible. He get to run loose per day, some areas I've him in a flexi, since it sometimes comes people and I don't have as good call-in as I would like to. People loving dog, it explains it all. I see how he lights up every time I let him out to do his doggy stuff, it does seems kind of pointless for humans, but the dog loves to explore and play around in the grass. For me, I would never had a dog if I couldn't let the dog go as he like, at least a couple times a week. I believe the dog would be kind of miserable going the same route every day, not get to sniff on stuff that he want to. But I can't help myself than to ask if a human really can make a dog happy and fulfill all his/hers need. Don't get me wrong, I'm all for owning a dog and to keep them as pets. I would be a miserable woman if I couldn't have dogs by my side. To get them to work with me and to be part of their herd. Most of todays dog wouldn't survive on their own either, so it's not a good idea to release them.

What does a dog really need? Would some dogs move away from their natural behavior just to stay with their humans? Can a dog be happy with just plenty of exercise and no or little contact with their people? How do you define a good dog life? Is their really a set formula for the perfect dog life? Tell me what you think, I would like to hear your side of the matter. A little brainstorming a thursday evening.