I would think he would have stood out but you never know, had Archie Moore stayed at 175 we would have lost out on some of his big wins and dominant heavyweight wins diluting his overall greatness. I think Sam's heavyweight fights accent his greatness and although he beat some great heavyweights its not to say he would have dominated 175lbs as a 175lber, James Toney in recent times showed us that he improved his game moving up in weight against heavyweights when he was somewhat past it at 175lbs
I'm missing something here, McG. You said " If he beat up Dillon, Levinsky, Kid Norfolk, Miske, Greb (!),Gunboat Smith, Jeff Clark, etc., he'd be very highly regarded now." And now you're saying he'd be less highly regarded now ? Did you mean if he ONLY fought the above mentioned list and avoided the HWs, he'd be merely "very highly regarded" compared to how he actually is regarded now ?
I'm saying that if Langford fought a different career where he fought at LHW and never at HW he would be highly regarded based upon resume, probably. But he would be less highly regarded than he is today because today he actually became a heavyweight of huge significance.