I don't like the question, it's poorly worded and probably was drawn up without much thought. The word 'iconic' does not necessarily imply positive qualities, but refers to how well-known or memorable the person is, and for that reason it has to be Bader, whom most of the public would instantly come up with.
If the question were worded in what I feel a more appropriate way, it would ask who is the most 'meritorious' or 'worthy' RAF figure of WW2, and that would elicit a different response. Guy Gibson would then have my vote, and not out of any disrespect to Bader, but I feel more is owed to Gibson than to Bader, brave as he was.
Who was the most iconic German figure in WW2? Adolf Hitler, I would think. Does that prove my point?