Well, there were plenty of graphics-based adventure games before Must, such as all of the Sierra games, like King's Quest, Space Quest, Leisure Suit Larry, etc.

Well, there were plenty of graphics-based adventure games before Must, such as all of the Sierra games, like King's Quest, Space Quest, Leisure Suit Larry, etc. After that, there were all of the LucasArts SCUMM-based games, before Myst arrived on the scene. Myst brought two new things to the genre - quicktime movies embedded in-game to make things come to life far more vividly, and the inability to pick things up - a constraint that generally lead to problems being more logical than had typically been the case for adventure games.