I felt Season 3 was okay when it was working as pitched and planned -- as an action-adventure show. However, within a few episodes of Season 3, the show took a very odd turn towards horror and fantasy with "The Dream Masters" and "Dragonslide," both of which essentially present magic, and this went to its nadir with "The Exodus" making the sliders' archnemesis a slasher villain akin to Jason and Michael, "Stoker" with the vampires and "This Slide of Paradise" which is unwatchable.
The problem with this sort of story for sliders: the characters are normal people who (more often than not) survive to get to the next episode and two of them are scientists. Scientists attempt to understand the underlying rules of existence and manipulate them. And you also have Wade, who understands sociological rules and Rembrandt, who understands artistic principles. Ideally, these characters would survive by acquiring and applying knowledge -- but when the magic and monsters and supernatural are uncontained by any rules relating to the characters, then the sliders end up solving their problems with force and violence rather than cleverness and it doesn't get to the heart of the characters themselves.
But if the episodes had stuck to the template of "Double Cross" -- technology, chase sequences, eye candy -- I think SLIDERS would have been okay. It would not have been the thought provoking, mind-expanding, satirical series of Season 1, but it would have been an enjoyable, acceptable, professional product. I also gently reject Torme's assertion that movie ripoffs should not be done on SLIDERS; I think SLIDERS is a perfect vehicle for pastiche. It'd be interesting to see the sliders devise a scientific solution to toppling dragons, defeating vampires, shutting down killer robots and step into other genres: the romcom, the conspiracy thriller, the espionage adventure, the office drama, the found footage episode, the documentary, the re-enactment crime show, the locked room mystery, and so on.
Unfortunately, Season 3 becomes overly fixated on horror and is also hit by a massive downturn in competence: scripts are clearly not reviewed before filming, budget is mishandled so badly that the back nine episodes of Season 3 are beset by financial shortages, actors misdeliver lines and yet those takes are aired, sound effects are missing from scenes.
Seasons 4 - 5, I don't really find all that different except Season 4 had the benefit of Marc Scott Zicree working on the first third or so of the season. Afterwards, the show becomes fixated on another genre -- the sci-fi technology drama. Pretty much every episode of the last two years is overly concerned with doomsday machines, computers, cloning, cryogenics data crystals, slideships, and this fixation on futuristic technology removes SLIDERS' charm as a dramedy focused more on sociology than technology.
For this reason, despite my personal fondness for the show, I don't really consider it "the best show ever" or even good. The first 22 episodes of the show are well-worth watching as a very grounded speculative fiction series akin to THE OUTER LIMITS and THE TWILIGHT ZONE but with a regular cast of lovable misfits. Everything after that is problematic in the extreme from its horrific chauvinism, its causal attitude to rape, its blatant hostility towards science whether it's aeronautics, archaeology, a baffling decision to waste money on a large and costly cave or hotel set that has to be included in the majority of episodes, the inability to retain actors who are contracted for six years, the overlong scripts that repeat already-established information to fill a page count.
SLIDERS is a personal favourite, but when I say that, I'm referring to the first 22 episodes and what comes afterwards, I tend to think of as a peculiar offbrand variant. It's unfortunate that to the public at large, people tend to remember SLIDERS for the bad movie ripoffs that were done with an incompetent charmlessness.