I'm with Zombie on this one, in spite of the fact that I hated Deion. I guess a lot of this depends on memory, because the stats don't tell much of the story with defensive backs. My recollection is that Deion usually shut down the opponent's best receiver. Was I just buying into the hype? I don't think so. I didn't want to believe the hype, but time after time I had to admit that the guy was just really, really good. I think he would be a Hall of Famer even if he hadn't returned punts.
Pack93z makes an interesting comment about how for a player to be iconic, he should be a complete player at his position. He was referring more to Urlacher there, but I've heard a similar criticism of Deion because he was poor in run support. I think most of the great players are well-rounded, but I do think it's possible for a player to be considered an all-time great in spite of being average or even deficient in some areas. An easy example would be Barry Sanders--not a power runner and not a particularly good blocker, but definitely one of the all-time great RBs.
Talent comes in strange packages sometimes. There are many examples of geniuses who had very specific talents and had shortcomings in other areas. I would agree that in football there is great value in being well-rounded, so that opponents cannot exploit one's weaknesses, but it's a team sport and that's what teammates are for. Because Deion could shut down the opponent's best receiver, he didn't need to be good at run support. His teammates could do that for him, and the trade-off was very much to his team's benefit.
It's similar with Urlacher. He's not strong at the point of attack, but the Bears have been very happy to surround him with stout defenders so he can roam the field and make plays. Asking him to be a traditional MLB would be a waste of his talents. I don't think of Urlacher as an all-time great MLB (it seems a little early to consider that possibility anyway), but I do think he is one of the best of his era.