The early home computers seem to be known mainly for arcade-style games and secondarily for CRPGs. Some of those are sure to figure here, because interest in them will overlap (and there was also an "arcade adventure" or "action adventure" marketing category).
However, I thought there should be a thread especially devoted to the "adventure" category, which seems to me most directly related to the early paper-and-pencil RPGs that were popular around the same time.
A vast number of such games were published, and (par for the course in almost any boom) most of them were not very good. There seems to be a general neglect of the field, though, and a self-fulfilling notion that "adventures don't sell" (especially those without graphical flash) became current among retailers and publishers.
Certainly they -- like wargames -- had a smaller market than some other types. For those who did and do like them, though, it can be a challenge to find out what the good ones are, apart from the most famous.
Please share your own favorites, whether from memory, from rediscovery, or even from getting at last a chance to play something via emulation.
For ZX Spectrum 48, I could put in a good word for at least... hmm... Head Over Heels, Heavy on the Magick, Lords of Midnight, Nightshade, Skool Daze, and Tir Na Nog. In some cases, their sequels and other related titles even improved on the originals in a number of ways (Doomdark's Revenge after LoM, Back to Skool after SD, Dun Darach after TNN...).