Well, the X Files was plagued by a typical case of diminishing returns. It just grew too predictible and empty over the seasons, and even at its best it was a bit hit and miss. The first couple seasons were decent and fresh.
I found the first season of "Once Upon a Time" (the fairytale world teleported into ours) to be exceptionally well written, even if the special effects are stuck in 2005 or so. The first episode was not the best, but by the third I was hooked, and they managed to pull off a well rounded multi-thread, ensemble cast based plot, with many interesting individual stories creating a unique world where even the overall story arch is paced and works right. Hope they get the second season right too.