Gerrard is nowhere near the world-class category. I think he is tactically limited (just compare him to Alonso) and loses posession in key areas too often. It's his eye for goal, his striking ability and his (usually) very high energy level that makes him valuable to any side in the world, but world-class is something truely different ...
Thats bollocks, otherwise you can level that criticism about Messi, Ladyboy, Kaka, and any offensive player who plays in midfield. Even though Gerrard lacks the discipline to play in a two man midfield (in Rafa's team), it is to his credit that he has so many other strengths to his game. This is the reason why he now plays as a second striker, to make use of his world class abilities, rather than his weaknesses.
Back to the topic, I don't like picking out the best player in the world in any position as there are often 2-3 claimants to the crown and everybody has their own opinion so I prefer to name players as "one of the best" rather than 'the' best.
Pepe IS world-class, and is in the top 3 keepers in the world.