Best - Grim Fandango, Monkey Island 1, The Longest Journey
Worst - Beyond Atlantis, Monkey Island 2, Dreamfall
I don't like endings that make me go "What the ..."
I can see how some people dislike the ending of Black Mirror, but
Spoiler: by the time that game was over, I was glad to see the end of Samuel. "Good riddance," was my final thought on that one.