The Berlin Tierpark has one of the biggest collection in europe, they had at the end of 2007 976 diffrent species, the Berlin Zoo had in January 2007 1439 species, Stuttgart has around 1000 species, Leipzig around 950.
Frankfurt had once a big collection, too. In the mid sixties, they had more than 900 species, unbelivable in this small zoo, they have only an area of nearly 30 acres.
And what left of the great collection of London Zoo ? Not very much, but they had no other choice, as like as Frankfurt Zoo. But the diffrence is, London has a big expansion zoo outside the City, Frankurt dosn't.
In the USA, San Antonio has a very big collection, too, and not to forget the Bronx-Zoo.