I would comfortably group Xavi, Modric, Pirlo and Scholes together, being similarly methodical pass masters, and would rank them in that order with Xavi the best down to Scholes the weakest. That is no slight on Scholes - this is a collection of the finest playmakers I have seen, absolutely mesmeric in circulating the ball. All of them are special players.
Kroos also fits into the 'dictator' category, but he is much more ordinary and doesn't really belong in a discussion about historically great controlling midfield players.
I don't think it's as straightforward to compare him to the rest, but if I was to slot Iniesta into that ranking it would be right in the middle, behind Xavi and Modric - I would have the latter over Iniesta in an advanced midfield position (while also coming closest to Xavi's level in a deeper role).
Gerrard and Lampard are just too different. I would group them (or Gerrard anyway) with other great powerful, direct attacking midfielders in Yaya Toure, Fabregas, De Bruyne and Di Maria. Gerrard was better than Lampard, but I have a hard time placing him amongst the rest of those names - all much of a muchness for me ( except perhaps Di Maria, slightly ahead - a sensational player in his best position). Despite the mismatch, I would certainly say that at the very least Xavi and Modric are just clearly better players than the two Englishmen.
Again though, I feel they should be on another list. As should Kroos. Having Xabi Alonso, Busquets and David Silva in place of those three would have been more fitting.