I own all the DVDs, a couple years ago I rewatched them. I may come off as a rabid fan at times but the background music was atrociously horrid. Also the story arc plot became overly convoluted and impossible to explain at times. That said, one of the most convoluted characters (Krycek) was my favorite. Aside from several minor valid criticisms like that, I really think it's a great platform for modern storytelling.
I do have to ask myself, at times, if there is some level of insane conspiracy theory today that we owe at least in part to those people watching X-Files when younger. I have to admit that the 9/11 inside job truthers movement claims could have been ripped from the pages of an X-Files script.
My biggest concern, of course, is whether or not it could still be fresh. With recent high quality additions to television canon, we'd have to be prepared for Chris Carter coming back at us with a 90's angle when episodes like Home really aren't as shocking anymore. The bar has been raised (thankfully).
Right now, The X-Files is going to occupy a contextual place in television history like The Twilight Zone. A revival could very well tarnish that. On the other hand, I've never felt like I really received closure on the whole story arc