You might ask whats my beef with modules, or why I think they are a primary cause of bad games.
First off, I dont need someone else to do my imagining for me (something gygax originally supported, until he realized the plebes would give him $$$); I already have too many ideas to actually put in play.
The real problem with modules is prep. I realize most people use modules because they think it saves them on prep time, but I believe that's a false assumption. Time is one factor in my poor opinion of modules, but it really comes down to knowledge of the material (which is why prep time is a problem). My first rule of DMing, which I try to impart to others but noone really seems to take to heart, is modified axiom from my college days: "know your setting, be your setting" (the original pertains to GIS, know your data, be your data). If you know your setting, every other detail of dming will follow. And this is where the problem with modules arises, because the module is written by someone other than oneself it takes a tremendous amount of labor to really know it and thus dm it well. Sure modules can be run without being overly familiar with them, but that usually leads to a very poor running and some degree of obvious railroading.
Essentially it comes down to the quality of game you want to run vs how much time you want to put into prep. In general, any game session I run will be better if I do a half-assed completely improv session, than if I do a module which I just skimmed through or read completely only once. And sure I can do a well-run session using a module, but at that point it must be practically memorized, and in the time it takes to get to know the module to that degree I could have prepared so much more material myself. And even the well run module will rarely measure up to my own material.
Now I can hear everyone saying that modules are a great tool for beginner DMs to learn from. I call BS. I've helped over a dozen(probably more, but I'm not really counting) players transition to DMing, and the most common thing I've found is that they all have a lack of confidence, whether running a module or not. Yet in all cases the dms who start with their own material tend to run better sessions(but let's be honest, every 1st time dm is pretty bad), and more importantly, they tend to stick with it and want to learn to be better. The desire to learn and grow as a dm is stifled when half the job is done by someone else; it's nearly impossible to really know the setting if you didn't make it yourself.
