He did not have just ONE good series. He has had three consistently good series against NZL, AUS and T20 cup. Plus his performances at home and his debut series against Australia in Australia.. these stats do NOT make him a one series wonder and prove that he can perform. Like it or not, he is the best opener we have and arguably the most successful one since Aamer Sohail and Saeed Anwar days.
Admittedly, he does not come anywhere near the greats you mentioned when it comes to class. But do not forget that moving ball makes everyone go nuts (lets not forget how brutally exposed Australian batsmen were in the last ashes despite being known as technically magnificent). Butt will struggle but he still has better chances and profile of succeeding than the likes of Hafeez, Farhat and Nazir). Having said that, he NEEDS to stop dropping sitters in fielding!
If we cannot appreciate a good performance and give credit when its due, we should not go overboard in criticizing a bad performance either..Looking forward to series in England though.. should be a cracker!