Zork (1980)
Sword of Fargoal (1982) (dungeon romp, like 20 years before IWD2)
Matrix (1982) (Gridrunner on LSD)
Fort Apocalypse (1982) (Choplifter go home)
Reach for the Stars (1983) (my first real xxxx game)
Oil Barons (1983) (yes, it was an effin big box with maps, counters and all)
Archon (1983) (battlechess, go home)
Jumpman (1983) (most fun platform game evar)
Boulderdash (1984) (addictive as...)
NATO Commander (1983 first "real time" strategy game. Bloody awesome too if you had the disk version)
Summer Games (1984) (slayer of joysticks)
The Lords of Midnight (1984) (first humongous open/sandbox world 1st person crpg and strategy game hybrid I remember)
Ultima IV (1985) (Not the shiniest graphics, but an interesting plot and a large world to explore) (sadly, I don't have my map and ankh anymore)
Racing Destruction Set (1985) (racing was never this fun before, nor after)
The Way of the Exploding Fist (1985) (still having seen a combat/action game that beats the "feel" of the moves and blocks)
Little Computer People (1985) (yes, Activision invented "The Sims")
Populous (1989) (being a god is quite fun)
and so forth and so forth...
Could probably write 3 full pages of games. A lot of the stuff by Epyx, Activision, EA, Ocean, Broderbund, Firebird etc. was pure genius pre-1990.
From where I'm sitting and watching, the gaming industry has been in a constant decline since 1989