I can’t say with 100% certainty, but I think it may have been King’s Quest 2, which is somewhat ironic since it’s one of my most loathed games from that era.
Most of my early PC memories are early Sierra adventures and while the nostalgia is strong,
man are those games terrible. They got much better later on, don't get me wrong, but the early ones are rough as fuck with dead-ends, poor writing and dumb puzzles. You all know it to be true.
Early Sierra adventures are a clear case where "you only like them because of nostalgia" is true.
Later ones were much better, mostly because they were designed by people who actually had some kind of idea about good game design (Jane Jensen single-handedly turned King's Quest into something good with KQ6, and then made Gabriel Knight, one of the best Sierra games).
Roberta and Ken Williams were good businesspeople and knew that using fancy graphics (for their time - as primitive as the KQ games look to us today, back in the day the graphics were considered amazing on a PC) would capture a large casual audience, but they were utter shit as game designers.