Actually, much of the Myst series' "eye candy" provided considerable depth, with all the journals and their diagrams, video segments, and (sort of) interactive points. While the environments were largely static (read: empty, dead), the back story found in the journals and other elements was interesting enough to keep going, at least for a while.
Depth in graphic adventures may be tough, but it's doable.
I disagree. Legend Entertainment managed to make some great "text & graphics" adventure games: Companions of Xanth, Deathgate, Shannara, and Callahan's Crosstime Saloon spring to mind. Perhaps it helped that they were all based on novels.
