I just never got what was so great about TESB. It wasn't a bad movie, but only in its context.
Now, it wasn't a bad movie. The plot wasn't that important, as it was simply the bridge between A New Hope and The Return of the Jedi. Characters needed to be in certain positions for the beginning of RotJ, and this movie got them there. In the meantime, George Lucas set about building the universe, which was awesome. There was room to explore characters, visit different worlds and explain what The Force was about. This is why I think TESB is such a big movie in Star Wars geekdom: it gave the series depth and something for the fanbase to get its teeth into.
The Holy Grail, though, was another thing entirely. It did seem to get a little clever for itself at times, but who cares? Barely a day goes by when I don't drop a quote from that movie, and I've only seen it twice. So it had a huge influence on me. For that reason my vote goes to The Python boys.