Greater fighter: Gennady Golovkin, Vasyl Lomachenko, or Sergey Kovalev

We have to factor size in when we judge how impressive a fighter looks at any level, including the elite level. It's much easier to be impressive and dominant against world level and elite opponents your own size, smaller or much smaller than it is vs ones bigger, much or way bigger who hold huge physical advantages over you or do so whilst also being big or huge punchers for their weight and size

When you're small or tiny for the weight fighting much or way bigger guys your own power is obviously less effective and your opponent's power is magnified than it is against opponents your own size. A lot less so

As excellent as someone like Crawford is, he's never fought anyone much bigger than him or with a longer reach, let alone way bigger than him with a longer or much longer reach who are KO artists or big punchers for a weight class he doesn't belong in. If he was routinely fighting world champs and top contenders who were 10-15lbs heavier than him with close to a six inch longer reach than him and/or ones who were much bigger than him and big or huge punchers he would not be near as dominant as he has been and the chances of him losing or getting knocked out would skyrocket. I'm not just singling him out because the same applies to every fighter doing the same