Well, the funny thing is these specialties are only competitive because of the American practice environment. 20 years ago, Orthopedics wasn't competitive at all. Dermatology isn't popular in any country that pays physicians similar salaries because what makes it great in America is $/lifestyle. If ortho reimbursement gets cut by 40% then people will flock to something else. Radiology is seeing an exodus right now while Urology is losing their PSA screening $. Competitive is synonymous with the best combination of controllable lifestyle, great reimbursements or private insurance/out-of-pocket payors, and low work hours.
The public doesn't know all the factors that make medical students so interested in specialties. They just see the superficial medical side (TV drama, technical skill, interesting procedures), hence they think Neurosurg seems really amazing and most medical students would avoid it like the plague.
Who knows what will be competitive 20 years from now, it depends on the technological advances and what the gov't decides to reimburse.