I was very much surprised when I first realized that there is actually CSI fanfic out there, as well.
For me Grissom/Willows, for instance, is not really a 'ship', but during the earlier seasons a thought of them pairing up crossed my mind. But I am a long way of following the series passionately and writing a fic about them.
My Mulder and Scully obsession was really an obsession in the late 90s. X-Files aired about six months behind US and I had to get my weekly fix of M/S in the site called "Institution Of The Relationshippers", where all shippy moments in episodes were written down. Man, I really got it bad back then.
J/C, which is stil going pretty strong after years and years of series finale. J/C fandom is so active and once they get you, there's no way of escaping. Especially when I am a post-Endgame shipper through and through.
There has not been other ships since J/C, which would have got me as hooked as I were with M/S and as I still somewhat are with J/C.