Being the most impersonated human being on the planet there's no arguing with the gigantic shadow cast by Elvis. As a solo entertainer and an individual icon he's pretty untouchable.
Plenty of music (as opposed to showbiz) fans play the "what if.." card speculating on the impact and influence Buddy Holly may well have gone onto achieve had he lived, but let's not overlook the argument that, had Buddy himself not heard Elvis in '55, his own sound would probably never have evolved and blossomed as it did. Certainly in his brief career Buddy produced more quality numbers than the (overrated IMO) Jerry Lee Lewis (two good songs) and Chuck Berry (one tune re-using different lyrics) put together. Little Richard could blow the lot of them (apart from Presley) off the stage anyway and was arguably a more palpable influence on the fabs than anyone...
Interesting to note that The Beatles never officially attempted an Elvis cover version? Did they perhaps feel this would have been sacrilege, whereas the back catalogues of Holly/Perkins/Berry/Richard etc were all fair game and ripe for sampling?
I'd put it this way: The Beatles loved Gene Vincent, Jerry Lee Lewis, Eddie Cochran, The Everly Brothers...
they adored Chuck Berry, Carl Perkins, Buddy Holly and Little Richard...
but they worshipped Elvis Presley.