Well I think that Muy Thai>>>>any other martial art in terms of real world use. One thing is that its very practical and it is perfect for how most fights really work. Flying/spinning kicks, flashy moves don't work. Self defense techinques don't really work. Elbow strikes, Knees, jabs, uppercuts, leg kicks/sweeps, headbutts, all at close range are what will win a real fight. On top of this, Muy Thai training has a lot of sparring and fighting, where other martial arts focus mainly on hitting air or pads(katas etc.).
Don't believe me? Look at the peole who win UFC now. The top ones use Muy Thai techniques/training and BJJ for the ground grappling. You saw how the karate experts got their butts kicked when they first competed and styles weren't the mixed like they are now. I truely believe that regular martial arts are not made for making you a fighter, more then making you better physically and mentally. You will be a better fighter if you are a black belt in TKD, but that doesn't mean you are a good fighter. Muy Thai is based on fighting and fighting efficently to knock out your opponent. Of course you will need some ground skills to be a good fighter, almost every real fight I have ever seen has gone to the ground, unless one of the people are VERY outmatched.