If we judge it on the 10/15 greatest players to come out of Ireland, then I would feel that Robbie is not in that list - some seriously great players we have produced. Each and every one of them really great players that should include the likes of Carey, Hurley and Cantwell as well as modern players from the past 30-40 years.
However, if we judge it on a player's contribution to the green shirt, Robbie easily walks into the top 5 in my opinion. He has scored 54 goals for a middle tier country. Yes some of them were against minnows and many were in friendlies, but he has been an ever present in our team for 15 years and a great example to young players in this country on how to conduct themselves. The likes of Gibson could take a leaf out of Robbie's book. You could compare Ronnie Whelan to Robbie for the purpose of this argument. Ronnie was arguably the best midfielder in Britain for a period of a few years and easily world class. On paper, he is one of our greats for what he achieved at Liverpool. However, in a green shirt, I seem to recall him often being poor or ineffective - in the same way Hoddle was wasted with England, Ronnie was probably wasted by us.
I'm not sure if some people are biased against Robbie because he is from Dublin - there is the Dub/country thing that goes on from a small element of our support, or others begrudge him being recognised as one of our greats because aside from fleeting moments and periods in his career, he never became the consistently world class player that he threatened to be when he was 18/19. Some maybe feel that he has made the easy decisions in his club career too often, like going to LA Galaxy.
However, regardless of what you think of Robbie as a man or as a player, he deserves to be recognised as a true Irish great.