I think MP was cut short because John Cleese got fed up and left - after that it lost some of its edge. I mean when ever people refer to classic MP sketches they hardly ever mention ones from the series John wasn't in.
He returned for the films and they were fantastic. And there was much rejoicing.
However this is
beside the point.
I find that there are many short running series that obtain a much better cult status in the following years than some more "successful" shows that went on much longer. However to be compeletly honest with you, I don't care if Futurama becomes a "cult" (It'll be great if it does) but I'd rather be watching brand new episodes of Futurama in years to come rather than remonising about the old ones.