The X-Men could do no wrong in my eyes until a few things started to bother me. The first was the Mutant Massacre. I had liked the Morlocks and thought they had an interesting place in mutant lore - and then Claremont inexplicably killed most of them. Why? You tell me. Whatever Sinister intended by killing off dozens of mutants, I'll never know. Does anyone know? Even the creators?
Worse than the slaughter of the Morlocks was that Claremont unceremoniously sidelined two of my favorite characters on the book (Kitty and Kurt). Sidelining Colossus was something I could deal with, but even he deserved better, in my opinion. They moved Kitty/Kurt/Rachel over to Excalibur, but it didn't feel like an X-book. I had no reason to care about Captain Britain or Meggan, before or after the Excalibur team came together.
Still, there were some good X-Men issues after the massacre. It was around Inferno when I realized Claremont didn't care anymore. That event also got rid of Illyana, who was a character I also loved. Somewhere around that issue, Claremont stopped writing New Mutants, and to say I didn't care for the next two creative teams is an understatement. After the Jim Lee explosion, I drifted away and stopped caring.
It's funny Kitty and Nightcrawler are my brothers favorite X characters but he loved Excalibur. Guess he felt like the focus of the book was on them rather then have them one of many in the main book.