Chimes in, off-topic, wonders where 3pp went wrong and wishes someone would make a decent video game under the D&D franchise. berates Dannyalcatraz for his lack of originality.
... wait, this ins't the Meta-Troll thread?
[On topic] For the better part of decade, I have had but one player in my group. We alternate campaign worlds, create new characters and new stories, and generally have a good time. I prefer to delve in 3pp and find all sorts of campaign worlds that I would love to run, but I have a tendency to want to try the Next Big Thing and each world I DM tends to be 'new' and unrelated to the last great campaign. My player, otoh, prefers to cherry-pick from various 3pp but generally sticks to his (ever-growing) homebrew world.
In short, we both run the kind of worlds we'd like to actually play in, and as such, we sell each other short in a lot of ways. He prefers more streamlined, traditional D&D; I prefer D&D at its later period(s), with steampunk, renaissance or even some sci-fi elements thrown in for good measure. While they're fun at the time, I get bored of the 'typical' fantasy world, and he isn't into the same 'weirdness' that I am. Further, I like to play with the crunch side of things at times while he prefers to just wing whatever he feels is appropriate, rules-be-damned.
As such, I have a mountain of PURE AWESOME 3pp that, for lack of a better reason, i will only ever introduce as a DM, because anything I intorduce into his world may not fit with his world vision.