It's not the Martial Art that matters ...it's the Martial Artist.
There's no such thing as the best system. That's like asking "what's the best colour?" A system that works well for some won't work for others. I have a couple black belts and there are a few systems I've tried where I couldn't even become effective at the basics because they were counter-intuitive for me and my body's range of movements didn't suit them.
It's all about how much effort you put in to understanding the art's applications. I've seen black belts who couldn't spar to save their lives, and I've seen yellow belts (beginners) who could kick as fast, and harder than me. Find the style that you personally identify with and train your ass off.
That's the best "system".
Ding ding ding!! We have a winner!!
Many here are focused on the school, yet ignore the individual and that is just as important.
What are your personality traits? You're physical traits/capabilities? What interests you in a certain style.
Using myself as an example...I am a rather passive person, short and rather heavy. As a result, I would find an aggressive form contrary to my personality. And while study and practice would counter some physical deficits, high kicking forms mightn't be the best for me.
Instead, Aikido is much better suited. A defensive form, focusing on throws and take downs rather than blows. A form where your feet seldom leave the floor.
Also ask yourself, "why do I want to learn a martial art?" Physical exercise? Mental discipline? Perfect body & mind? (And by perfect I don't mean ripped and chiseled, more of state) Self defense? Beat up the guy down the street? Shear curiosity?
I started because I was curious, but found I enjoyed the technicality and the combination of mental and physical. I quit due to no school to attend near by, and now have long term (unrelated) injuries to contend with as well.
Though we do have a local Tai Chi school...