If you do more than sit on the couch all day, BMI is pretty useless. It would call derek poundstone obese. On the other hand, its much more than how you feel.
I have a very different opinion on what fitness is than a long distance runner would. The whole thing is too subjective for a single definitive answer. Health has very little to do with how you feel though. You may not even know how bad you feel until you get healthier.