For MT, I no longer keep up with it very closely but here is a good list to start from:
Saenchai, Payakaroon, Worawoot, Silachai, Ploenchit, Khamsing, Thanasukarn, Kaennorsing, Sit Hrun, Put Lorlek.
Saenchai is possibly my favorite to watch. He's like Sakuraba or an incredibly motivated BJ Penn in that he fights at many different weights and is ridiculously skilled. Payakaroon is the goat. Watch any HL vids and fights of these guys.
Lastly, be very wary of anyone who says Buakaw Por Pramuk is an all-time great in MT. He's not even remotely close but he is possibly the most recognizable MT figure worldwide. A loose analogy would be someone like David Beckham in football.