It was the X-Men #1 "Blue Team, Gold Team" group. "Strike Force X-Men was a name Wizard magazxine used forever ago and I always liked it, because it captured exactly what was different about that team compared to what came before and after. The weren't kids, students or teachers. The Xavier Institute wasn't a anymore school. They were adults on a big team of mutants, whose job it was to protect the world from mutant and non-mutant threats. They were organized and at the height of their powers.
You had Cyclops who finally came into his own after the end of X-Factor and losing his son to Apocalypse.
You had Wolverine, who cotemporarneously in his own book at the time, was first being fleshed out with the entire "Weapon X" back story (Marvel Comics Presents Weapon X came out at a similar time). This was Wolverine at the start of his run as the 1990s most popular comics character.
You had Jean Grey, finally post Phoenix, at the height of her capability.
You had Gambit and Rogue, who moved way past what they debuted as in the years before.
You Beast as a peer to Xavier, and an Xavier who was involved and motivated.
You had Storm and Colosuss at the height of her powers and position in the X-Men, leaving behind weird 1980s stories.
Iceman and Archagel moved well past their X-Factor incarnations.
Bishop came along before too long.
You had NINJA Psylocke who started her run as second to only Wolverine in combat ability.
Originally you had Forge and Banshee too.
This is the X-Men that decided to actively attack Magneto. Twice.
It's worth recalling how they came about. It's a merger of the 1980s X-Factor (the original 5), the Australian X-Men (Storm, Wolverine, Psylocke, Colossus, and indirectly Gambit and Rogue) along with some Muir Isle X-Men (Forge, Banshee) and a returned Professor X. Havok (Australian team) joined X-Factor, which replaced Freedom Force at the government's mutant team (Freedom Force really being Mystique's Brotherhood of Evil Mutants, legitimized). Polaris and Multiple Man who were associated with the Muir Isle X-Men joined X-Factor. Rachel Grey / Phoenix, Kitty Pryde and Nightcrawler founded Excalibur and left the Australian team just before they became the Australian team (Fall of the Mutants crossover). And of course, the New Mutants had just met Cable and were transitioning into the first X-Force.
It was and remains the best X-Men era, and everything that's come after has been a pale imitation brought about by writers who didn't think long term about what to do with these characters and their world. The X-men being in Chris Claremont's hands for 16 years, uninterrupted, brought about the "Strike Force" team.
But now days you got "Pixie" and Rockslide, and Beast being an imbecile and Cyclops (until recently) becoming essentially, Magneto, complete with Magneto Island. And you have a Wolverine whose back story is not arguably Marvel's most explored. You have the Gay Iceman retcon.
Uncanny X-Men is doing a back-to-basics kind of thing snow, with Cyclops in his 1990s uniform for the first time in nearly 20 years. But it's going to get all undone this summer with Powers of X and House of X, which will be yet another radical revamp for a franchise that's only suffered because of it since Messiah Complex.