Not sure, but it should be. I've been playing 2k5 and 2k8 mainly.
I go to Lions games at Ford Field often and you always hear the ROOOOAAARRR! after a big play (not many roars last year..
) But when I play madden and make a big play, there is no Roar. Seems like stadium specific sound effects should be extremely easy to implement. I'm surprised they left it out for so many years. Makes me wonder if the audio guys on the Madden team are much of football fans.