very interesting post.
i gotta disagree on federer having a weak surface and borg not having one. fed has multiple clay titles and more than a handful of clay finals, where he has lost to the beast that is rafael nadal on clay. borg, otoh, never won a us open, despite (like you point out) being at the top of the game-top 3- for 8 years. overall, fed is pretty dominant on clay except when he plays rafa.
i do agree, however, with your view of the Aussie Open back then; it just wasn't considered a huge slam, like today. borg would 've won a handful, presumably, not to mention the fact that bjorn retired at 25.
Cyborg, your emphasis on being at the top for long time (not just 3 or 4 years) has got me thinking. If Federer continues to lose points and falls to #3 or #4 or worse within the next 4 months, his GOAT status will become jeopardized to my mind, at least.
Like you say, Borg was top 3 for 8 years. Federer was throwing rackets and tantrums until 2003 and although still #2 in early 2008, looks to be headed downward, as he can't beat the de facto top 3. See 0-10 record against Nadal, Djokovic, and Murray, in last 10 meetings.