Dan Meth did a great job creating his own personal Trilogy Meter showing his personal enjoyment of movies released as a trilogy.  This shows that Dan never likes the 3rd movie as much, so he should just stop spending the money.

Although this is based on Dan's personal ratings for each movie, there's no reason why something like this couldn't be done with more official data like critic ratings or box office dollars.

Thanks for the link Jesper and Daniel!