Man, that question is too hard! The first thing that popped into my head was "The Best of Times" by Styx, but I think that's just because it has the word "best" in it...
And then I look again and see Metallica in your post, and I think "nono, One is better!", lol.
So I dunno...the best song depends on what I'm listening to at the time, kinda like my favorite snake is the one I'm holding