Loma in terms of cutting off the ring and creating new angles of attack, don't think anybody does it better than him in terms off offensive footwork. Ali in terms of defensive footwork, constantly on the move, playing with range and moving laterally at great speed. No heavyweight could move like he could for 15 rounds.
Can’t believe no one has mentioned the great Joe Louis. The Brown Bomber came from the boxing philosophy of balance, from HOF trainer Jack Blackburn. Anyone who watches Joe Louis knows his footwork was the epitome of efficiency.
He did have great footwork, excellent balance, pivoted well to create angles, great positioning etc. But he didn't have the quickest, lightest feet and I think most people when they think of footwork think of fast agile fighters, which really is only a part of one aspect of good footwork, Louis' footwork can easily be missed by those who don't know what to look for beyond fast, agile feet.
I agree with those, who said Muhammad Ali. I've never seen anything like the young Ali, before or since.