must play games, from any genre?
Star Control 2 - Amongst the best games of all time. Unique game...not exactly part of any existing genre. Combines exploration and RPG with some excellent script writing, great humor and great music in a galaxy with real-physics space combat.
Princess Maker 2 - Sort of like a cross between Tamagotchi, Alter Ego and Pretty Polly Dress-up, packaged in a psuedo-RPG with some unique elements. You raise a daughter from age 10 to 18 to see what kind of woman she will become. Will she marry the prince? Will she become the Queen of Hell? Or just an ordinary housewife? I'm not kidding, by the way. QUeen of Hell is one possible ending. This game isn't a tentacle hentai game but neither is it a game for 8 year old girls. It is cute and adorable, but still a real game that was taken seriously by the designers. Play under dosbox, and absolutely make sure that you get sound and music working.
Phantasy Star 4 for the Genesis console - Standard console RPG, but with some of the best writing in the genre. This game will be especially epic if you've previously played some of its prequels. There were lots of years between the first and the fourth in the series, and the people who wrote 4 obviously cared a great deal about the original games, and filled 4 with a great deal of subtlety and humor for oldschool players. This game made me cry. Several times.