Here are my top 10 X-Men runs from 60 years of comics, trying to represent everything from the Bronze Age on. Some are longer than others, and really I should separate these into more granular chunks, but 10 is a nice round number.
- The classic '70s and early '80s Claremont run, collected in UXM Omnibus #1-3. This is the period where anything was possible, and the artists were helping plot the series to attune with their strengths. (For instance, John Byrne is great with sci fi, Dave Cockrum is great with lighthearted adventure, and Paul Smith is great with character drama.) Almost all the key stories of the X-titles have their roots in this run.
- Claremont and Bill Sienkewicz's run on New Mutants in the mid-eighties. Again, this involves a writer who wanted to get weird and exploratory, and an artist who is best at dreamscapes, combining to get the best qualities of both.
- Inferno Prologue & Inferno from the late '80s. This is Claremont and Simonson acting in the kind of cross-title harmony that is way harder to pull off than it looks, with the plot coming to a head in all 3 titles without ever feeling tacked on or phoned in.
- Alan Davis' Excalibur in the late '80s and early '90s. First as artist, then as writer/artist, Davis adds whimsy and fun to a romp through increasingly elaborate alternate universes with the lighthearted X-Men that actually ends up going somewhere.
- The launch of adjectiveless X-Men in the early 90s, under Claremont/Lee and Nicieza/Kubert. Nicieza decides to double down not only on the purple prose of Claremont and the constant pinup poses of Jim Lee, but the byzantine subplots and deep cuts from X-history as well. He manages to make something that's enjoyably cheesy, not just eye-rolling.
- Grant Morrison's New X-Men. A reboot with a fresh take on the franchise, some genuinely new and cool ideas, and a sense of wonder. His Magneto is pretty bad, but Claremont wrote some terrible issues, too.
- Joss Whedon and John Cassaday's Astonishing X-Men. This story manages to synthesize Claremont, Morrison, and modern comics writing, while also delivering an engaging plot.
- The Messiah crossover series (Messiah Complex, X-Force, Messiah War, Necrosha, Second Coming). These are the rare example of crossovers done right, using a giant cast to up the stakes on a single driving idea and move the characters forward. Kyle and Yost get to use their talent for grimdark stories and shock value to full effect.
- Peter David's second run on X-Factor. David is at his best in the early issues, fusing his usual self-aware jokes with a noir procedural format to tell a series of fun and engaging stories that get a lot of mileage out of C-list X-characters.
- Rick Remender's Uncanny X-Force. Remender combines the character study amidst chaotic circumstances of Excalibur with the shoot-first, Deadpool-friendly ethos of New X-Men and X-Force to tell a moving story with real character development that somehow doesn't lose any of the shock value or lurid violence.
Anything I left out? Let me know!