Be interested to know how the data was collected and the definition of spectator.
Is it Tv audience?
Is it attendance?
If it includes both I'd dispute the Eire result for starters
And does Rugby include both codes as one? As I find the Aussie result a tad perplexing too
In terms of actual attendance, marginally more people watch Gaelic Football then Football according to the most recent ESRI report on sport in Ireland (6.1% vs 5.5%), which is in itself a few years out of date (2009). Not bad all things considered.
Of course, in terms of participation, football comes out well on top. In TV viewership, only the largest GAA games (All Ireland Finals & Semi Finals) compare to the big Ireland WC & EC qualification games. When Ireland are actually in a tournament, or more likely are in a play off, they tend to be the most watched TV events of the year.