So many to choose from!

I'll say (in no particular order):

1) Space Quest III (hilarious and fun!)
2) The Colonel's Bequest (loved all the death scenes!)
3) King's Quest VI - a masterpiece!

P.S. I wrote Roberta Williams a letter back in 1992 or so (when I was in high school) and told her I wanted to get into computer gaming. She wrote me back! She was traveling in India at the time with her husband Ken, and gave me some tips. A hand written letter - need to find it. Classy lady!

1) Quest for Glory
2) Space Quest III
3) The Colonel's Bequest

I love text parser games.
Point and click is good, but text parser is best!

Well I've only actually finished one : Police Quest 1

If I had to ask my future self who's finished more of them, then he'll probably say:

1.) Police Quest
2.) Police Quest 2 (Played this one a little bit at a friend's house back in the day and it was great!)
3.) One of the space quests

I am not listing any Dynamix/Sierra games, but "pure" Sierra games. Also I haven't properly played the later Sierra games, like after Space Quest 4 and King's Quest 5. Anyway, my top three:

1. Space Quest 4: Good humor, good story, great Roland MT-32 music and sound effects!

https://www.youtube.com/watch?v=jf_jICoLcGo&list=PLDB654C9F8064B9FD

2. Space Quest 1 VGA remake (not on GOG apparently): Pretty much the same as above.

https://www.youtube.com/watch?v=Ej-KMC-T0l8&list=PL527D39E1742D2A44

3. King's Quest (the original): This is here mainly for nostalgic reasons. I was a wee kid when playing it, but damn it was a magical game, playing it on a IBM PC machine. A whole world to explore, things to try out etc. I had to ask my big brother to help with English language.

1. Quest For Glory IV
2. Quest For Glory II (EGA)
3. King's Quest VI

I chose these off the top of my head. Narrowing it down to three games is somewhat limiting, given how so many of those adventure games appealed to me in various ways. The QFG series has a decided edge over KQ due to the increased replayability, combat elements, and the decreased likelihood of dead-ends and unwinnable states.

Hmmm....

1. Quest for Glory IV Shadows of Darkness
2. The Beast Within: A Gabriel Knight Mystery
3. Phantasmagoria

GK1
Phantasmagoria
GK2