Added Ultima to the list of famous series. Hero's Quest/Quest for Glory probably also deserves a mention, as a hybrid between graphical adventure and CRPG.
Also, I don't know that I'd call CRPGs "adventure games" in general; while a lot of them do have a similar story progression or use objects in an "adventure-game" way (some of the Ultimas feel like simulationist graphic adventures at times), the essence of CRPG-ness seems to be quantitative development of your characters' abilities. [JeffPack 23Aug02]
Minor grammatical tweaking made for consistency with glossary formatting. [AmandaButler 18Nov02]