This debate always end up falling apart because 'World Class' is just a poorly defined term, don't think I've ever seen a discussion about it go even remotely well. The team a player could get into is heavily determined by what type of team that is. Almost all the players mentioned have been 'world class' in a specific team, and even a present decline doesn't necessarily indicate it is them rather than the team or system that has changed since then.
Think a discussion like this you just need to take the approach of things like the Guardian's top 100 footballers and as said somewhere earlier go with top 30-ish players who you'd throw into the hat, because the order beyond that is never going to be universally agreed upon.
Would identify Ramos as of the big game heavy weights though, can't deny the guy has turned up.