Allman Brothers live at the Fillmore is absolutely one of the best, but picking the top three of that era, at the Fillmore, just isn't possible because you've left out Derek and the Dominoes and Humble Pie. No way any list of enduring live albums from NYC in '70 &'71 can exclude them. I'd suggest going with a top 5.
I agree with the Humble Pie assertion. It was a seminal live recording and the last with both Marriot and Frampton.
The Dominoes recording not so much as they did not have Duane All man at that show and he was integral to their original soun .