140: Gatti for sure. Corley is highly underrated. Both these fights were offensive exhibitions. 147: Got to be Marquez or Hatton. I'd go with beating Marquez by 13 points in a 12 rounder at a weight he would go on to make big noise at... He's got a lot of other real solid top wins at WW, but all of them could be argued to be behind his three victories up at JMW.
I wouldn't really call the Marquez fight a big win.. Sure, Marquez was the p4p number 2 fighter in the world and sure Mayweather was at a year and a half layoff.. But Marquez is 3-1 at WW and was the Lightweight champion of the world during the Mayweather bout. I'd honestly rate the Judah win higher than the Marquez win.
beating marquez, is like pac beating rigo at c/w between 135 and 140 and pac not honoring the c/w. hows that sound? good win for pac?
I was going to say Oscar, but I just remembered that bout was at 154. Handing Hatton his first stoppage. Mosley also deserves a mention, given his early scare. At 140, Artoro Gatti would fit the bill. While never at the very top of world level, Gatti was a formidable opponent and Floyd utterly dismantled him in a one-sided beatdown.