This is objectively false, not just a matter of opinion- what made Jean Grey popular was Claremont's portrayal of her and the Phoenix storyline. And the only reason those two happened was because , unlike the rest of the X-men that left that series after GSXM, she had to appear in the book regularly because she was Scott's girlfriend, so Claremont decided to give her a different portrayal and a cool storyline. If Jean wasn't dating him, she would just go to Limbo like Havok and Polaris, or go to Champions like Angel and Iceman and be cancelled after 20 issues or rso.