It was released in 1989, but preceded by Nether Earth
In general, I wouldn't add any 'second parts' to the list, because they obviously can't be the really groundbreaking ones. 75% of Speedball 2 for example is just Speedball "1"! That also goes for 'informal' follow-ups like Quake (covered by Doom or Wolfenstein 3D) or Master of Magic (mixture of Civilization and Master of Orion).
For Adventures, I'd like to nominate Adventure
(or its extended version Colossal Cave Adventure