It almost goes without saying that the original Zork trilogy is a must-play for most interactive fictions enthusiasts. As someone who is relatively new to the medium/genre, it was gratifying to play through the first part of the trilogy (and then the sequels) after I had experienced some more recent works first. This set me up to have a whole bunch of "Oh, this is where that came from" moments as I played through Zork's underground that would have been lost on me otherwise. The narrative style of the game works really well for me when paired with a sense of vague familiarity.
The modular structure and dubious geometry of the underground may not earn the game points for realism, but I enjoyed mapping the maze-y areas with Trizbort while playing. There was also never a sense of "What do I do next?" at any point, I think due to the clear association of specific rooms with specific puzzles and functions. The puzzles themselves were hard as hell, but gratifying to complete.
While the game is obviously littered with ideas that become genre tropes and conventions later on, there are also some things that I am glad didn't stick. For instance, I never would have completed the meta-parser puzzles (e.g. (Spoiler - click to show)the cyclops and echo puzzles) without using a walkthrough. The (Spoiler - click to show)sceptre puzzle was also maddening, seemingly requiring knowledge of previous games and/or a willingness to brute-force every possible command into the parser.