Veron, Sanchez, Hazard, Di Maria, Shevchenko, Toure, Aguero, Van Nistelrooy, Van Der Saar.
OK a range of peaks there, but that's a sample of some of the world's best players.
I do see your point though. It's not easy to get the world's best to England.
Spain Vs. England
Better weather
Amazing food
Barcelona has the beach
Barcelona is a beautiful city. London has its pluses, but it's less homely and bad weather means it's harder to enjoy as regularly
Spanish women are generally much hotter and in better shape.
Relative economy is worse off which means better off for footballers in Spain as get more for your money, e.g. property.
England Vs. Spain
More competitive football
Weather is more comfortable for running around in.
More variety of food
Arguably higher worldwide league status if that really matters, although higher twitter and facebook followers generally equals more money!
Bottom line Spain has big advantages that are unlikely to change.