Its not about creating in general....because obviously they generate a lot of assists.
Its very simple...they are both amazing attacking players...forwards...wingers...strikers...whatever you want to call it.
However only one of the two can drop deep and control a game from there. Messi shows this even more with Argentina. Cronaldo for me completely lacks this part of the game...and in some of his play its completely absent when he takes on players or shoots when a team mate is clear. He blew a couple of good breaks for Madrid by doing this.
He simply doesnt have the Xavi/Maradona/Zidane/Pirlo part of the game in his makeup whereas Messi certainly does.
And again...who knows how Messi would do in another team. Nobody. We can only judge them on what they do and have done on the field in their careers so far.
By the way I dont think either of them have been at the same level as before since the start of last season despite the amazing goal tallies.
