So many bad endings, I agree with many posters in this thread. But for me
Golden Gate has the worst ending of all. I don't want to spoil the game for anybody, but if you're not interested in first-person Mystian puzzle games with FMV flashbacks you can safely read my spoiler:
Spoiler:You're a treasure hunter. When you finally find the treasure in a cave near the beach, another treasure hunter you've met before appears and while you listen to his long and boring monologue, the tide comes in and the water starts filling the cave. The last thing you see is the water closing over your head and the rest is darkness. You drown, you stupid fool! BWAHAHAHAAAAAAAAAA!!!!