Twin Peaks was probably the best show ever made. It managed to find a way to balance almost every genre possible into one series and it's had a significant effect on television since (on shows such as X files, 24,and Lost). One thing that Twin Peaks does require though, is patience. Some people watch a little and just can't take it. They say it's too weird for them or it's not obvious enough. So, you could also say it's an acquired taste. However, if you have an open mind, then I highly recommend it. What originally got me into TP was the brilliantly trippy Black Lodge scenes. I've never seen anything like it. I was instantly fascinated and eventually watched the entire series when I found it on youtube. However, a lot of people simply dismiss those scenes as stupid. Again, it's an acquired taste.
X Files was definetely inspired by it, but not as good as TP. X Files was inspired by its mythology but it often tried to hide itself as a "safe" procedural-esque monster of the week type show (much like Smallville) in order not to chase off viewers.
Admittedly, TP does fall off in season 2 once the Laura Palmer storyline is solved but (again, if you're patient) it only falls off for a few episodes and then it quickly rebounds back to where it was before into a fantastic finish with a great villian in Windom Earle and a new love interest.