I like this kind of debates, Gerd, so allow me to extend a little on my point of view.
I understand the logic of that line of thought, but in my oppinion is flawed. Basically because the only way to assess how good is a player is to watch him play at top level, competing against the best. Very talented players may be unlucky to play at lower divisions/countries than they should, but at the end the luck/opportunity factor is an important part of the equation.
If someone is playing at Malaisia, I don't care if he was unlucky, he never reached top level competition for a reason, wghatever it is. Luck/opportunity plays a big role on careers. May seem unfair, but it's how the world works. What about the best player in history that nobody knows because he got severely injured? Would Pele be considered a top player if he was born in Angola?
So, removing all the "what if" of the equation, let me focus on another thing. Yes, Xavi, Iniesta and Busquets were great players, but you should know that for nearly 6 years they didn't win anything, they weren't even starters for the team. It was Pep who made them shine in a deffensive system that focused on keeping the ball to cancel the opponent. But the X facotr was Messi breaking the defenders at the right moment. If you dig into statistics, you will see that the team has won many things without Xavi and Iniesta, but has hardly won any single important match without Messi.
But it's very easy to test this. Do this if you have some time: go to Youtube and choose ANY year of Messi's career. Look for the Messi highlights of that season, not just goals, watch for assists and highlights in general. You will be astonsihed, I assure you. Most people has seen only what he did in key matches, but if you see what he did EVERY week for 8 years... I tell you, in a single year, he has done what took other players their whole career. Then you multiply that for all the years he's been performing at that level, and then you realize the bloody monster he is. It's not only the goals, or the assists, it's his total dominance of all aspects of play, from passing to dribbling, finishing, shooting, his vision... something no one had done before at that level for so long.