I think you can get legend status in a few ways - achievement, cult status, club loyalty, or a mixture of them. It is easier to pick them from the past as not only did we win more trophies but players generally stuck around for longer.
I don't agree that Arteta is a legend - he won nothing and pushed for a move from the club. Cahill is for his longer service and the fact that he carried the team on countless occasions. Hibbo probably is as a1 club man and his inability to score.
Big Dunc has a claim as he loved the club with a passion. Can't think of anyone else who really deserves that tag from 90s onwards.