Seasons 1-5 of X-Files are just fantastic, 6-7 are of variable quality, 8 is mostly bad and 9 is dreadful. If your Best Beloved doesn't like the treatment of Scully in S1, though, she may not enjoy the rest of the series. My absolute favourite season is Season 5, but a lot of that plays off having seen earlier seasons - 1 and 2 are the only two that really stand alone.