If I remember correctly, Myst was a pioneer (if not revolutionary) in a number of areas:
1. It was one of the first computer games that were distributed with CD-ROM.
2. It was THE first computer game that was distributed ENTIRELY with CD-ROM.
3. It was probably the first computer game outside the racing/flight simulator/FPS genres that emphasised a first-person perspective.
4. It was probably the first computer game that used pre-rendered 2D backgrounds.
5. It was the first adventure game that isn't dialogue-based or inventory-based (it has a small inventory, but mainly for storing documents rather than tools; if I remember correctly, the first Myst game has only one "tool" that can be "used" at the end of the game). Myst was exploratory. The player wasn't told to achieve any goal.
It also remained as the top best-selling computer game for a half-decade. Its sales record (six million copies) was surpassed only by Half-Life and StarCraft in 1998, five years after Myst was released.