What is the best overall martial art?

What system of Martial Art is "best" is always a matter of opinion. What makes a Martial Art good is if it provides training that helps the individual student improve in many aspects, including fighting skills and character development. The system of Martial Art is usually not what makes the training better or worse, but the quality of instruction based on the knowledge and expertise of the teacher. Ultimately, the effectiveness or success of using any particular Martial Art depends on both the accuracy of instruction, and the abilities of the student to perform it correctly. The "best" Martial Art for any individual is the one that you try and like at a school where you enjoy training so that you will stick with it for a long time.

It should be understood that sport versions of Taekwondo, Karate, Judo, or MMA ("Mixed Martial Art") are not Martial Art systems in and of themselves, but games played according to a set of rules. They might contain elements of the original Martial Art from where they originated, and share the same name, but the actual Martial Art is not limited by rules, and does not focus on one aspect of kicking, flipping, or ground-fighting, but utilizes techniques and tactics for all aspects of self defense, plus character development, morals and ethics. Combining fighting skills and adapting to the latest developments is not a new concept as this has been done for centuries, and Jeet Kune Do and MMA are just the latest fads to market and popularize the wisdom and methods of ancient masters of genuine Martial Art systems.