If you have a diagnosed illness, then your service dog should probably be considered "real." I'm not as confident as you that most of these people have diagnosed illnesses, however.

I know a guy with a traumatic brain injury that is confined to a wheelchair and has a "real" service dog. I don't think there is any way you can train a random dog to this level on your own. The dog has amazing skills and took many months to train. Also the trainers select dogs that exhibit the right temperment at a very young age.