Realistic or not, greats are measured by championships. Some say Tom Brady is the greatest quarterback of all time because he has been to six Superbowls and won four of them. However, people argue that Joe Montana is better because he won four without losing any. They discount the fact that Brady took his team to two more because he lost them. Peyton Manning continues to have his story rewritten because a defense won him his second Superbowl, so now the "greatest regular season quarterback" is his tag.
Look at the most recent NBA Finals. People were saying losing and going 2-5 in the Finals, despite being there 7 times, would knock LeBron out of a lot of top 5/top 10 players of all time lists. But, going 3-4 by winning suddenly puts him on the same level as Michael Jordan.
Winning is more important in the general eye than talent when it comes to placing people on their sport's Mt. Rushmore. It is a bit sad, but is what it is.
But why only international tournaments then? Messi's club competition record beats both Pele/Maradona.
The biggest and baddest prize of them all? No one is calling a former XFL or USFL player the best American football player of all time. Either that or stubborn people who refuse to believe anyone can surpass their heroes. Hell, he can win the current tourney and there will still be people complaining that he has yet to win a World Cup so it doesn't count until he does.
It's just a bad way to see it. Joe Monatana didn't win the championship by himself, Brady didn't win championships without some well rounded Pats teams.
Plus the obvious catch that for an NFL player the only big title to win is the NFL itself. Real football is more complex.
I wouldn't say soccerfootball is more complex from a title perspective. World Cup is your biggest and baddest. That's the ultimate prize right there. Harder and more noteworthy? Absolutely. More complex? Not for a commonplace fan looking for someone to win on the grandest stage of them all.