Hi all,
if we talk just about length, the Berge Stahl (nor the A whale) aren't the biggest.
The container ship Emma Maerk is 397m long, and the longest (sold for demolition at this time) was the Knock Nevis (458,45m after modifications). Even the Queen Mary 2 is a bit longer (345m) !
And the biggest ship ever build (The Knock Nevis has become bigger only after modifications) was The Pierre Guillaumat : http://www.aukevisser.nl/supertankers/id38.htm , 414m length.
A "fun" fact is when you read the Pierre Guillaumat was build in 1977 ... And scrapped in 1983 !
a few comparisons : http://en.wikipedia.org/wiki/File:Bateaux_comparaison2.svg