Las Vegas - Floyd Mayweather rounded on his detractors after beating Mexico's Juan Manuel Marquez with a unanimous points decision on his return to boxing on Saturday.
"I'm never going to win," Mayweather, 32, told a post-fight news conference after dominating his first bout since coming out of a 21-month retirement.
"When am I going to get my just due and people just acknowledge that Floyd Mayweather is a great fighter?"
The American has been criticised in the past for avoiding some dangerous opponents and he was loudly booed by a majority of the 13 000-strong crowd as he made his way to the ring in the wake of the hugely popular Marquez.
Although Marquez was a world champion at three different weights, there was criticism of Mayweather's selection of a former featherweight champion, who had most recently fought at lightweight, as his opponent for a welterweight bout.
That criticism intensified when Mayweather failed to make the contracted weight of 144 pounds on Friday, instead tipping the scales at 146 pounds, four pounds heavier than Marquez.
"To be the best, you got to beat the best in your era," said Mayweather, who was back in the ring for the first time since his 10th round stoppage of Britain's Ricky Hatton in Dec. 2007.
"It's not about weight classes. I came from a small weight class too."
Mayweather won his first world title in 1998 at junior lightweight, 17 pounds lighter than the welterweight division in which he now competes.
The smaller and lighter Marquez, 50-5-1 (37 KOs) said: "I tried my best but the weight was a big problem.
"I think there was a 20-pound difference in weight," he added, referring to the fighter's respective weights on Saturday. "The weight was an advantage but Floyd's a great fighter.
"He's very fast and a very good counter puncher. I came to fight 12 hard rounds and a lot of people thought I was going to get knocked out. But I wasn't and I hope I made Mexico proud."
Mayweather, who improved his career record to 40-0 with 25 knockouts, paid tribute to the gutsy display by the Mexican.
"Marquez is tough as hell," he said. "I hit him with a couple of shots and I thought: 'I know he's going to go from this one', but he kept coming."
Immediately after the fight ended, Mayweather was challenged by fellow American and WBC welterweight champion Shane Mosley.
"I'm hoping that the best will fight the best," said Mosley. "That's what the sport of boxing needs.
"I'm the number one welterweight champion out there right now and I'm the type that's willing to fight anybody. I want to clean up the division so everyone will know I'm the best fighter."
Mayweather refused to be drawn into any speculation about his next opponent.
"Tonight's not Shane Mosley's night," he said. "No disrespect to Mosley, but he's supposed to be in training camp, not worrying about me. All roads lead to Floyd Mayweather. Everybody wants to fight me. I can't fight everybody."