Try an English soccer game sometime...there are freaking 30-60,000 people singing all kinds of crazy crap. West Ham's "Bubbles" and Liverpool's "You'll Never Walk Alone" are probably the best.
You'll Never Walk Alone always sounds like it's being sung by drunk people. Just the nature of a huge crowd singing it, as they slur the words. But they are pretty epic, but I have no clue how you would build a tradition like that in American sports.