So... what are your lists of truly great adventures you've run? (Or played in, if you're a player...) And which potentially great adventures do you want to run?
Cheers!
Traveller: Adventure 2 (Research Station Gamma), 3 (Twilight's Peak) and 12 (Secret of the Ancients) - which are functionally an adventture path from 1979-1980... They present a different kind of view of the setting than...
Traveller: The Traveller Adventure. A half-inch thick Letter sized 6 to 18 month campaign, And the campaign that brought the Marches to life for me as a GM.
The combination of those (and they can be worked in together to one even longer campaign) is what brought The Spinward Marches and the 3rd Imperium to life for me.
ALIEN: Chariot of the Gods
ALIEN: Destroyer of Worlds
Both managed to capture the tone of the movie series, both manage to make the adventure interesting, and both have replayability. They both can be as little as 8 to as many as 40 hours of play, depending upon players, their curiosity, and the GM's indulgence in the many side-tracks they allow for.
Pendragon: The Boy King. A campaign spanning up to 100 years... and putting the players into the heart of Greg Stafford's then-vision of Arthur's legendary story...
Pendragon: The Great Pendragon Campaign. Same basics, better details, more adventures and adventure seeds.
WFRP 1E: The Enemy Within.
I'm in my 6th run of it? Yeah. Never had a single party make it all the way through, tho' i've run the whole thing across several runs.
WEG Star Wars: Otherspace and Otherspace II...
These are great for when a party just totally «bleep»s up the astrogation roll.... I've reused them in FFG star wars, too...
Sentinel Comics Starter set. Took me 13 sessions for the 6 included adventures. Teaches the game excellently, and provides several different kinds of adventures. One didn't work for one group, but did for the other group; the other 5 worked well for both groups.
Firefly: The Wedding Planners. Every time I've run it, it had different modes, but in every case, it was a fun time and love triumphed over money and power... thanks to the PCs. And in one case, Vera's twin...