This is it for me as well. And the Paul Smith "era" was only 10 issues.
But yeah the Smith and JRJR runs are peak X-Men for me. Of course I like the entire (first Claremont) run a lot, though I'm not a huge fan of Inferno or Outback era. But it's all good.
The early '90s, Jim Lee/cartoon era is a strong second, just because that was when my fandom was most activated, even though I objectively know that the early/mid-'80s Uncanny stuff was better, and I reread that stuff a lot more than, say, Fatal Attractions. But '90s X-Men gets shat on unnecessarily. Lobdell and Nicieza were solid replacements as cruise-control Claremonts. You had generally great art, with the Kuberts, Joe Mad, Pacheco, Bachalo. And I never liked them that much at the time, but stuff like Operation Zero Tolerance and the Phallanx Covenant were like better than any X-overs after them except like two (Messiah Coming and Second Coming).
I like the Morrison run a lot but it seems more like a "saga" than an era. To me I can't really get comfortable with it as an era because every bit of it is very much part of a narrative that Morrison was driving toward. Calling it an era would be like calling the Dark Phoenix Saga an era, and that feels wrong. I liked what he did and I liked the extended cast, even the weird mutant kids worked for me.
Whedon's run was great but it was just superficial nostalgia porn.
For the side series, of course I like early New Mutants, up until the 30s or so especially. I like any issue of Excalibur that Alan Davis had anything to do with. PAD's X-Factor (any run) is okay but often overrated IMO. Nicieza's X-Force after Liefeld leaves (sorry Rob) is generally underrated. I could never get into Generation X much, despite having like 70 issues of it, but Bachalo's art was nice at times.
And yes holy hell X-Treme is underrated. I own the whole series but haven't had time to read all of it yet. That's going to change. Sexy sexy sexy sexy stuff.