1975 was before my time as a fan (I was a baby!), but 1991 is my biggest disappointment as well. Worse than 1993, as difficult as that may seem. At least in 1993, they got to the Finals. What also made 1991 so painful was the fact that the Kings lost to the Oilers. It has been so long since they've played in the playoffs, and the current Oilers have been so bad for so long, that it's hard to imagine why that would be. However, the Kings-Oilers rivalry was uber intense in the 80's and early 90's. Nothing from today even comes close (Kings - Ducks? Give me a break).
By the way, I'm pretty sure John Muckler was the Oilers coach in 1991, FWIW.