"I Have no Mouth, and I Must Scream" is based on the short story of the same name and had the rare privilege of counting the original writer (Harlan Ellison) among its contributors. As such, it could be considered a complement to the original, even if some details were changed or toned down for the final release.
I think having each character face a unique scenario tailored after their own personal flaws was a great idea and the graphics are still pretty good even after all these years, a certain creature in particular remains horrifying.
The game is not without flaws, however. It's possible to beat certain scenarios and the game itself with sub-optimal choices, but that also means that getting the best ending is a matter of following a guide because otherwise you wouldn't know that you missed something in one of the scenarios until it's too late. There's also a couple of instances of pixel hunting and having to walk back and forth in order to trigger certain events and progress. It's far from the most obtuse game in the genre, but these are issues I thought were worth mentioning.
Overall, I think "I Have No Mouth, and I Must Scream" is pretty good, but that's more due to its phenomenal writing and set pieces than the quality of its gameplay.