There won't be another band like them, ever...
I've been a Maiden fan for 6 years and let me just put it this way: there's no band like them, and there never will be a band like them. This is why I love Maiden... The first time those dual guitars, heavy bass and soaring vocals crash out of your speakers, it's like your first kiss.
Their music hasn't changed radically over their career, but they've taken their sound and tried bunch if new things with it. They've gone in a different direction with every album yet it still SOUNDS like them. It's like Rush, I don't listen to a lot of Rush past Moving Pictures, but show me a clip of a song of theirs and I'll recognize it as Rush. That's what bands should do in my opinion, stay true to who they are. Their lyrics are about war, religion, honour, fictional works and life in general. The way Harris and co can tell stories is simply stunning; listen to "The Talisman" and you're hooked by the opening line: "As I stand and look about the port/And contemplate my life/Will I ever see my countrymen again?"
Ah what the hell. I'll just end it here: if you haven't listened to them yet, go buy an album right now. and see them live too. They're simply the greatest band in existence.