Oh and I should define: an "anthem" would be 6 minutes plus in length, the longer the better, with at least a 2 minute instrumental. Shorter exceptions exist like "the thrill is gone" don't quite make the time limit, but are anthems none the less.
I take issue with your definition, sir!
It's hard to argue that "We Will Rock You" is not an anthem, and it's <6m, IIRC. I also don't think that a song should be DQ'd on account of not having an instrumental bit.
Jay Z's "Ghetto Anthem" certainly wants to be an anthem. Fight For Your Right To Party by the Beastie Boys has anthem written all over it, but so does that whole album. Rhymin' and Stealin' and No Sleep 'Till Brooklyn jump out at me.
Come to think of it, all of that Rick Rubin produced rap is some kind of re-mixed rock anthem. I'd say that Jay Z's 99 problems (R.Rubin produced) is more of an "Anthem" than "Ghetto Anthem".
Least anyone dismiss me as one-dimentional, I'm keenly aware that classic rock is the home of the anthem, and it likely always will be. Voodoo Chile takes the cake ("Chop it down with the edge of my hand..."), but there's so much going on in there anthem-wise. "Piece of my heart", "Break on Through'. Sh*t, how 'bout "Peace Frog"?
Imagine is kind of an anthem, but I'd say a different kind.
Largely, it's all about theme. The song ought to be epic. Themes of heroism, high on emotion... the songs that just kick ass and make you bleed from the soul.
For what it's worth, I'm going to be in an amateur boxing match this coming Sep. 10th. It will be my first and likely my last. A charity fight to raise money for my rugby team. After careful consideration, my entrance music will be "Can't You Hear Me Knockin'" by the Stones. An anthem if there ever was one. I picked it because it comes on strong right away and never lets up.
A list of other songs that I personally consider anthems, and that you might want to look up:
Know Your Enemy - Rage Against the Machine
Attitude - The Misfits
Somebody to Love - Queen
(Bigger than) Hip Hop - Dead Prez
Long Way to the Top - AC/DC
Come Together - The Beatles
Evenflow - Pearl Jam
Like A Hurricane - Neil Young (this is only a borderline anthem)
Gin and Juice - Snoop Dogg
Kick out the Jams - MC5
Excluded from the list, but still my personal theme song: (Get on up, I feel like being a) Sex Machine - James Brown