Farscape, hands down, for the sheer imagination they showed. I love the way Zhaan was painted, and then there was Stark's face sans mask (ewww). Natira, with the eyeball plucking tendrils on her head was particularly impressive.
In my opinion, the best make-up was Star Trek the Next Generation, just as you've shown in the photo above. It was always unique, expertly done and never looked greasy as some make-up looks under film lights.
I think Star Trek: The Next Generation showed just how far they had come over the years.If you compare some of their early make-up to the make-up and prosthetics in the later seasons, you'll see the progress made leaps and bounds. For that reason I'll go for them.