LOL! I love their Flying Circus skits, omg. The Spanish Inquisition was fantastic. I still shout that a lot! Lmao.
Also, The Holy Grail would be my top favourite. As a kid I always loved medieval things, and well, the Holy Grail. Lol, so naturally I loved it. And their humour is cleaner in that one, more like the Flying Circus.
Meaning of Life was so-so. I made the mistake of watching that as a kid. I was like "WHAT IS GOING ON OH GOSH." Lmao. Bad bad idea.
I never watched Life of Brian, only because I'm religious (Christian), so I was like "ehh I probably won't find it that funny." But that one's just based on bias, of course.