To you. Which is fine. But there isn't a general definition for it. And additionally: Aren't Buchan and Robson rather the exception than the rule? We have to keep in mind, that supporters are from very different agegroups. Another poster told me that he learned about a few legends via his grandfather. I personally have no connection to some of the names. I don't know Buchan, so he'll never be a legend in the way Scholes or Rooney are. Not because they were better, but because it is more tangible what they did and achieved.
Think it is safe to say that SAF would have had a few ideas how to make use of him. Think, he'd be a fine second striker back then as well.
Oh no doubt about it. I'd never argue against that. But for me, and seemingly a few others, that isn't enough to be considered a legend.