It's gotta be Monkey Island 1 or Day of the Tentacle or Sam and Max or Damage Incorporated or Thinking Things Collection 2, then I was "upgraded" to stuff like Zoombinis, Marvis Beacon Teaches Typing (for kids), a mathsy puzzle game and Step On It, Solitaire, Tomb Raider 1...
I do not know which is the earliest, but if you grab the first that came out chronologically, that should get you pretty close - I am going to guess Prince of Persia.