Dunno, hard to quantify in these days where cruise speeds and levels are managed to generally minimize cost per flying hour….which means more than just fuel enters into the equation.
This is all hand waving, rough impression stuff but from what I experienced over the years:
The 747 batted along pretty darned quickly,
The earlier big twins were slower, for the 777-200, maybe, generally .02 or .o3 Mach slower than the 744 ish/thereabouts in the cruise.
The 777-300 things started to speed up a bit again but not quite to 744 speeds.
Got the impression certainly the 380 and maybe the 787 could rattle along at 747 speeds…
In response to DRs point I was merely commenting on the last 30 years, he / the article are absolutely right that 60 years back some airliners cruised at what by modern standards would be regarded as
Mach numbers..for example the Convair 880