I've owned all three. I never liked the FM, especially when saddled with its unreliable motor drive. It was the least "Nikon-like" Nikon I had ever used (I started using Nikons with the original F/FTn models). I believe the FM2 was an improvement but I had no experience with it.
I had an early F3--before the F3HP was introduced--and I truly despised that camera. The electronics were so poorly sealed it would quit working under even slightly damp circumstances. When it worked, it was great--light and very ergonomic. But I couldn't rely on a camera that would stop working in the middle of an assignment. Later models were much better sealed and better built but the early F3 was the camera that caused me to buy my first Leica.
The F2A is a different story. Tough as a hockey puck, smooth as butter, reliable to the extreme. I still have two favorite F2 bodies from those days that I will cherish forever even though neither have been used in nearly 25 years. I loved all the F2 models and still consider the F2 to be the best 35mm SLR ever made.
I have to point out that I worked for a daily newspaper during the time I used these cameras. The cameras were used heavily, often under extremely harsh conditions--conditions to which most normal everyday shooters would never subject their equipment. If used more conservatively, I'm sure any of the mentioned cameras would be more than adequate.
