I’d argue the last great/essential X-Men story was the Hope saga. But then they got painted into a corner with the “evil” Cyclops. Bendis was supposed to revamp the line but I think he got sidetracked by the emergence of the Guardians of the Galaxy craze.
Honestly it’s time for a reboot. At least at DC this would be the logical solution. Marvel seems to have played everything out and now they’re just beating their ideas to death. Someone will say, well that was what the Ultimate comics were. And I’ll say no, the Ultimate comics were about accelerating the classic Marvel approach in a modern context. Except in the quirk-by-design titles, it’s tough to have fun with a Marvel comic. The grim era of the 70s and 80s never culminated for Marvel the way it did at DC, so in a lot of ways we’re seeing what happens when it extends too far. The movies won’t be drawing from the comics being made right now. They built on the stuff being done a decade ago, because that was a golden age for Marvel. Stuff after that, even as early as the Future Foundation, doesn’t exist, because Marvel started reverting heavily to form but without actually changing track. It makes no sense, and it makes perfect Marvel sense. But that’s how I see it. Personally I would’ve liked for the original Young Avengers to have taken over, them and maybe the Runaways. But subsequent creators working on those properties seemed to have no real clue about what made them work.