Good post!
I don't like the way some of these labels are used, but Peter Whittingham is certainly a club legend. There may be half a dozen players who fit that category in the whole history of the club. It shouldn't be used lightly.
When it comes to 'cult hero' Robin Friday clearly fits. It isn't really about ability or attitude or longevity, but about the way he is remembered. The iconic image of him flicking the V, the myths and stories that grew up around him, the 'anti-hero' and sad elements of his life away from the pitch and changing room all contribute to the cult status.
Then there are fans favourites who may just fit the 'cult hero' definition - not necessarily the best, but part of the club furniture with a massive connection to the fans: Earnie, Chops, Super Kev in recent times.