Yes, they are defintely comic geniuses. Some of the material was a bit boring, but mostly there is some very intelligent and original material. A good example of some of their best stuff was in the Holy Grail. The Life of Brian was great too. The show itself wasn't perfect, but generally each episode had some good skits.

As for some of my favourite skits:

-Spam
-The skit about the dumb boxer with John Cleese
-Summarize Prout in 5 minutes
-The Spanish Inquisitition

to name a few. I forget some of them now.