The X-Files built up a loyal cult following during most of its first season, read low ratings, and from then on has appealed to slightly wider audience. Initially I thought this wider appeal would inflict a mortal wound on the story but fortunately it didn't.
Throughout The X-Files there is an air of "sexual tension" between Scully and Mulder, and some have suggested that their attraction for each other should be made more concrete. Many, including myself, believe that it would ruin the tension which has built up over the years and would send the show down the path trodden by Moonlighting. The tension allows the two agents to throw subtle daggers at each other, and adds a lot of character to the show, a character which is sadly missing from many of TVs "serious" dramas.