(I consider ALL of the below to be United legends, but I've split them into two groups. The second group consists of players who I have experienced people disagreeing with me on multiple times. So don't shoot the messenger!
)
More or less undisputed United legends
Edwards, Charlton, Law, Best, Robson, Schmeichel, Giggs, Scholes, G.Neville, Irwin, Keane, Cantona, Cole, Stam, Rio, Vidic, Rooney
Seems to be up for debate
Beckham, Solskjær*, Evra, Park, Carrick, De Gea, Ronaldo**
* his reputation (unfairly) took a blow after his managerial stint
** (rightfully) fell down after his second stint
The only thing these all have in common are Premier League/English First Division trophies. Some are there primarily because of their hard work, others for their x factor. Some were at the club for a long time, others for just 3 years.
There are multiple players on this list that Bruno is more talented than. There are multiple players on this list that Bruno will have stuck around for longer than this summer. And in terms of hard work and effort, Bruno does in no way look out of place. The only way to exclude Bruno (provided that you agree on the second group as well) is if you consider winning the PL a necessity in order to be considered a legend. Personally I disagree with this distinction so regardless of happens in the upcoming years Bruno has already done enough to warrant a spot in that second group.