Sheeeeeit... was gonna say Alice won the thread in the second post but then Simonka ups the ante with the trump card to end all trump cards.
Elfen Lied is unbeatable.
This doesn't really count since its not technically an anime OP, but if they ever did an animated version of Sayonara wo Oshiete with the original theme it would win by default...
Also, the animated opening to Daicon IV (anime convention in the 80's) by the guys who would go on to form GAINAX is also pretty stellar