Both Messi and Iniesta are great footballers, but not the greatest of all time. I'd put Maradona and Pele ahead of Messi. As for greatest midfielder, there's only Zidane for me. I'd definitely place Iniesta in my top 10, but I find it hard to rate players in this era so highly, as the competition isn't as tough. The top teams are too OP, and the gap between the best teams and the rest is ever increasing. You just need to look at how mediocre international football, not just club football, has become to realize the diminishing quality. I used to enjoy watching the World Cup, seeing stacked Brazil, Argentina, and even Italy teams. Now, a solid and industrious Germany is doing well, but there aren't really any standout players on that team; they're a great collective, but that's about it.
Messi has failed his country on countless occasions, Ronaldo's Portugal win in spite of and not because of him, and teams like Brazil, Italy, and Holland look a pale shadow, a cheap imitation of their former selves.