Just adding my love for the Tunnels of Doom. Released in 1982, it can best be described as an upgraded version of Rogue. Random dungeon generation, first-person hallways, non-combat interaction such as fountains and vaults with secret passcodes, random magical items, listening for monsters at doors, this game had nascent versions of alot of the features that people now appreciate in rogelikes such as Nethack, but with graphical sprites and color which, in 1982, made this game freaking awesome.

I did my thesis in exactly this area. My research assumed that task complexity had something to do with enjoyment, but I was wrong. Experimental evidence showed that people had more when the difficulty of the task made the outcome uncertain relative to their skill level. This jives with researcher Kevin Burns theories of enjoyment being derived from unexpected good news (the unexpected occurrence of positive information gain) - i.e. the punchline of a joke or winning against the perceived odds.