Yeah, it's a great song. I remember the first time I heard it as I was listening to the album for the first time, and it immediately struck me as pretty special (I was in the parking lot at Topanga Mall in Woodland Hills, CA waiting for my wife and listening to it on the car stereo). That said, I have tired of it a bit from hearing it played live so much. That doesn't make it less of a song. But it does make me less inclined to want to listen to it.
Interesting call on Gangland. I'm not sure I would say it is their "best." But it is a really cool, creative take. At the time I got that covers disk, I don't think I had ever heard the original, so I was pretty intrigued by how different it sounded from the rest of the album. I don't want to say I was "let down" when I finally heard the Maiden version. But I was surprised, that's for sure.
Regarding Octavarium: It definitely has some tracks that I know can be in the lower tier on a lot of fan rankings. If you happen to fall on the side of not liking most or all of those, I can see how it might be your least favorite album. For me, it has a couple of my least favorite. But it also has some of my most favorite as well, so it's really a mixed bag. Overall, I think it's a great album.