Most of them, with few some notable exceptions, originates from Asia. The ones that I listed are all stand up fighting styles with a different level of effectiveness. But there are other combat sports that are not based around stand up striking like BJJ - Brazilian Jiu-Jitsu - and wrestling. I will also compare them to Muay Thai and demonstrate how mixing them with Thai boxing will produce a more complimentary martial art.
The biggest distinction between Muay Thai and aforementioned martial arts is that Thai boxing is built around 8 points of contact: punches, elbows, kicks and knees instead of 2 for Boxing or 4 for Kickboxing, Taekwondo or Karate. This is a very important difference since knees and elbows are one of the toughest parts of a human body and it is very little that can break when hit.
Muaythai also implements clinch techniques which not only allows the fighter to control the opponent in stand up but also helps him to initiate a devastating knee and elbow strikes.
Muay Thai and boxing are somewhat complimentary since many of western Thai boxing schools implement traditional boxing techniques into a standard Muay Thai training. I have been training in one of those gyms and I have to admit that western boxing is more effective, especially for Europeans and Americans, than traditional Thai punching techniques.
It's just more powerful and explosive than Muay Thai boxing based on straight arm jabs and crosses. Click on this link to read more about Western Boxing cons and pros.
One thing that Muay Thai and Western boxing have in common is that training and learning are implemented into sparring sessions. You have to face a challenging opponent and adjust your approach and techniques to be able to withstand a real fight. That doesn't apply to Karate or Kung Fu, where students are more preoccupied on repeating same patterns and polishing particular moves on their own. Click on this link to read more about Kung Fu cons and pros.
One of the best indicators of what works and what doesn't are MMA competitions.
Useful techniques are used more often and the less effective ones are being discarded.
So what is the state of MMA today? What styles are the most dominant in cage fighting? It all boils down to BJJ and Wrestling for grappling techniques, Boxing and Muay Thai for stand up striking and Thai Boxing + Wrestling for a clinch game.
There are some exceptions of course. One of them is Cung Le, who is a Taekwondo striker and a successful mixed martial artist that doesn't utilize wrestling skills.
I remember watching his fight with Ken Shamrock, a very skilled wrestler, in which he broke Ken's arm with his powerful TDK kicks. He was a powerful kicker and one those fighters who prefer to keep their opponents on distance. That said, if he utilized more wrestling skills in the cage he would be a complete fighter.
Click on this link to read more about Taekwondo's cons and pros.
Also take a look at Muay Thai techniques: