Icons v Legends v Greats...
For me there needs to be a distinction between Icon v Legend v Great v Club Stalwart (or a different term) .. you need almost 4 tiers of greatness in order to differentiate which player is deserving of more praise and respect than another. I apologise if the terms I use are incorrectly defined i.e. some might see the term Icon as being of a lesser status than the term Legend but just assuming that Icon means more than Legend.. this is how I see it.
Icon
I would define an icon of the club as someone who transcends merely footballing achievement, demands worship almost to that of a deity.. a god like figure at a club. You not only identify him with the club but when you think of the club, you identify it with him.. the player is that legendary, he is part of the building blocks of the United myth. The sort of player who inspires you to support the club, the star man, makes you take up the sport of football as your first love, one you will research like mad.. he represents Manchester United as an identity in your mind. He must also be universally acclaimed, be beyond reproach and appeal to all generations. Statute worthy.
For me the following players are icons of Manchester United... Meredith, Edwards, Best, Law, Charlton, Robson, Cantona, Keane, Schmeichel*.
Possibly including Giggs/Scholes.
Ronaldo and Beckham were for me iconic figures during their tenure here, Rooney and Giggs also had the opportunity to become icons.. but all 4 fall short for me. Ronaldo simply didn't stay long enough to be an icon of the club, he could have been this clubs greatest ever player and 'The' man you associate with United.. during his time here, he was the star attraction and the reason why many enjoyed watching United.. but he left far too soon to be part of the United myth. Beckham, when I was growing up was the most recognised of the 'best midfield unit in the world'. He was also alongside Keane the main man in that midfield, he was the least talented of that quartet but he had a confidence in his ability, a swag to his game which made him a formidable threat and he and Keane were truly world class in a mental sense.. they would not be found wanting at any level of football. He too left too early and it can be argued he just didn't have enough about his game near the end to push on and still be the star man.. the game was leaving him behind and he left perhaps at the right time.
Rooney and Giggs, two british wonder kids...both could have been the best players this club has ever seen but due to injuries, inconsistency never really became the star men in their sides at any stage during their United careers. Both were essentially, world class support acts but were never depended upon to lead the club to trophies.. both have produced iconic moments, Giggs v Arsenal for example but moments aren't enough, you need to be relied upon as the main man to be an icon.. someone to rally the team around and neither satisfied that criteria. My exclusion of Giggs might be seen as controversial, so I might be persuaded to put him down as an icon due to his longevity, which is iconic in of itself.
Scholes .. Scholes for me was unfairly perhaps never seen as the superstar of Manchester United, yet for the likes of Xavi etc he was an idol.. a reference point for what a midfielder should be like. He was also consistently world class for United, but for me an icon needs to also transcend the on the pitch stuff and be a big cultural/media reference and he was simply too quiet off the pitch and not enough of a star player on it to merit being an icon. Pirlo had teams built around him both at club level and internationally, which allowed him to earn iconic status but for me Scholes despite being equal to him as a player never quite demanded that level of respect from his managers.
Schmeichel for me is an icon due to his position on the pitch, he's the best goalkeeper United have ever had and he along with Oliver Khan were the the greatest keepers of the modern era, they transcended the position of goalkeeper to the point where they were considered captains, icons globally... like Casillas for Real Madrid yet they were greater both as men and keepers.
Legend
Giggs, Scholes and Irwin would be at the forefront of this group of players which in my opinion includes Beckham, Ronaldo and Ferdinand to name but a few. Again it should be restricted to truly great players who achieved legendary feats for this club and were key figures in writing the history of this club. I think Ronaldo was a legend purely because he was 'the' not just 'a' key component in our 3rd CL victory and our return to the forefront of European and domestic football. Lets not forget that post 2002... many of us were wondering whether United were ever going to match the success of the nineties and whether Chelsea would leave us behind. Ronaldo was the symbol of our resurgence, the reference point for that period of success.. once he left, we struggled on.. winning domestic trophies by the skin of our teeth but it became workmanlike, it was not the stuff you write about 50 years from now.. whereas the success from 2006-2009 was the stuff of dreams, the best football in the world was being played right here at Old Trafford and it is because Ronaldo was playing for us.. only one other footballer could have brought that same level of dynamism and electricity to our side.. and it was Messi, or Ronaldinho before him.
Beckham for me also deserves legendary status.. why? look at the list of number 7's before and after him.. yet was he ever seen as an inferior number 7 during his tenure here? feck was he, he was lauded as one of the world's greatest players and this was reflected in his runner up awards in the Fifa world player of the year awards where he finished second to Rivaldo. He was the world's most recognised footballer during his time here and helped this club become huge all round the world, much of our global success can still be attributed to the brand that Beckham helped build United to be..it was on the back of not just his looks and glamour, but his style of play.. look at Schneiderlin's interview where he talks almost in awe about Becks.. for most of us young fans, we all went through that phase.. he was the man for many of us and he never really enjoyed success post us, so he is still ours.
Rooney.. possibly gets in on the skin of his teeth, but not for me though. In the 2010/11 season he was a talisman at the key moments, throughout his career he has been extremely erratic and has never led us to glory on the back of his own brilliant performances. In the two campaigns where he was truly talismanic and brilliant we won feck all, was that his fault? or was he let down by the performances of his team mates.. one has to say he produced some mesmeric moments in his time here but again nowhere near the iconic moments others have under extreme pressure against the world's best clubs.. he does however have a CL final goal to his name. If he becomes the club's leading scorer, I think it is only fair he is named as a legend but there will always be an asterisk against his name for many, for a variety of reasons on and off the pitch.
Great
For me this where the likes of Steve Bruce, G. Pallister, Mark Hughes, Solksjaer go... great players, great memories but not quite of the quality of the men named above. Rooney most definitely gets into this category but a guy of his quality should have been an icon, not struggling to obtain legendary status. It is a shameful indictment of his failure to get the most of his talent that his status as a legend is even up for debate.
It is where I would put Van Der Sar, Vidic and Evra. An elite band of footballers but possibly didn't stay at the club long enough, or weren't renowned enough as the superstar of their team enough to be classed as a legend of the club. When you look at Maldini, despite being a defender.. he is still an icon for AC Milan, but for me these three players despite being the bedrock of our success from 06-12.. were legendary as a group, but individually I do not think they quite merited being called legends in their own right for what they achieved at United. Van Der Sar is rightfully remembered as a footballing legend, one of the all time best keepers for me but didn't stay enough at United to be a legend here.
Stalwart/Ambassador
This is for the best of the rest including cult figures. Players who deserve to be recognised for their service to United, are part of the United dynasty and brand.. your Nicky Butts, Park Ji Sungs etc.