When it comes to the art of striking, Muay Thai is hands down better than any other style out there. While there are other effective striking styles like Dutch Kickboxing, for example, there is nothing as complete as Muay Thai.
The reason Muay Thai is the complete stand-up art is because it utilizes 8 limbs to attack. Instead of just punching and kicking, Muay Thai fighters are able to use deadly knee and elbow attacks. In addition, Muay Thai fighters are also masters at clinching (stand-up grappling) and are able to throw their opponents to the ground.