I would say Supernatural & Into The Future are the two least essential. IMO, the paranormal and science fiction elements of The Sims work best in small doses, as a gimmick off the beaten path. This is why I really enjoy playing as a Simbot or alien, but rarely play as the life states from Supernatural. Supernatural and Into The Future oversaturate the game with the more farfetched elements of the series, and to me, that detracts from their appeal.
Neither of them are poorly executed; they work as fun gimmicks, but I rarely use them as part of my regular gameplay unless I've completely exhausted all other methods of having fun with the game. If do begin to lose interest, I begin travelling to the future, winning the lottery several times over, building Plumbots and bringing them back to the present just for some OP ridiculousness before I drop the game for a few months.
There are some items from ITF that I use on a regular basis - the wardrobe, dresser and coffee table, to be exact. I like the ultra-modern aesthetic, and ITF provides some of that, though I mostly rely on High-End Loft Stuff. I've never cared for the gothic aesthetic of Supernatural.
I regret voting for ITF now, because upon further thought, if I had to pick one of the two to jettison, it would have to be Supernatural, simply because I prefer science fiction over fantasy, and as aforementioned, I use the pack's features on occasion.
In terms of pure quality, Showtime is the worst EP, significantly. It seemingly existed exclusively to facilitate the Katy Perry brand deal. But, I still use a few of the items from the EP on a regular basis, thus I cannot call it unessential.
