Updated: Jan 11, 2021
Different people get different things out of playing and gamesmastering an RPG. I enjoy the process of actually running a game very much - the challenge of having to think on my feet, ensure what's going on is clear to all my players, keep the action flowing smoothly and respond to any unexpected moves or decisions the group may make (to be honest, the sense of power appeals to my megalomaniac streak as well).
I have to confess that I enjoy the process of writing and preparing for scenarios at least as much, though. A couple of years ago our group spent eight or nine months playing Adventures in Middle-Earth, and while the group had a good time, I have no particular memories of that campaign. Why? Well, Middle-Earth is a setting I've just never been able to get my head around writing RPG scenarios for - everything seems so oriented around Tolkien's particular story in a way which isn't the case with other fictional universes. So (uniquely) I bought a published campaign and ran through that, pretty much as-written.
It seemed to go okay, but I missed spending time between games coming up with scenario ideas and building the ongoing story of the campaign: it almost feels like gaming away from the table, and if my games are successful (my players assure me they usually are) it's because I know the scenario situations backwards, having cogitated on them for so long.
In short, I like to write my own scenarios, rather than use published ones. That said, coming up with new ideas while time is pressing can be a challenge - it's possible, but not a lot of fun. Often, rather than coming up with a whole scenario concept from nowhere, I'll steal an image from one place and a setting from somewhere else, with a possible plot spine from a third source, and put those together as the basis of the adventure I'm going to run.
For this reason, I'm more a fan of those little collections of adventure hooks you sometimes get in supplements and zines, than of full scenarios written out in detail. The chances are I'll probably end up extensively rewriting the scenario to suit my campaign and player preferences, to the point where it ends up unrecognisable. I'll probably get three or four times as many usable ideas from a collection of hooks as I will from a full scenario of twice the same length.
This is the main reason why the freebie I offer to all subscribers to the Near Window email list is a collection of scenario seeds - basically it's twenty adventure hooks, but with added suggestions about how they're likely to play out, how they could be adapted for different settings, and what potential problems could crop up while running them. I've used them to run many Call of Cthulhu sessions for our group, but they're system-neutral and should be easy to adapt to most horror RPG systems.
If you decide to use any of them, I hope you have fun! I'd love to hear about how you got on.