I think you have some good ones in there but it really depends on what kind of game you consider to be great or do you like all types of adventures?
Without knowing what you prefer, I'd consider these on your to-play list as ones that I would start with:
Shivers - Effective atmosphere, music, puzzles.. some tedium in moving around and the whole one-inventory item thing can get annoying.
Riven - I'd venture you aren't a huge Myst fan if you never played Riven. Tough game but beautiful.
Morpheus - Kinda grainy graphics (if you're picky) but solid, not-too-tough puzzles and an interesting storyline.
Faust - I liked this game a lot for it's non-linear story telling. Decent puzzles and graphics. Unique choice of music.
Traitor's Gate - I have to play this as well but I hear it's good... but I've been told its sequel is garbage.
Lighthouse - Myst-clone that's a big challenge and may be too hard to be fun for some.
Return to Zork - Want some rye? Course ya do! Quirky.
Hope that helps some
