Don't get me wrong, I love Zep and Sabbath, but when it comes to rock bands, I have to go with AC/DC.
They weren't very original. They weren't all that creative. Sure, they're albums are tough to tell apart. But holy crap, they rock like no others.
As for good bands from the late '90s and '00s, I need to add Dropkick Murphies to my list, I am ashamed that I forgot them. Punk/Hardcore/Irish music from Boston, Mass. I still need their new album, but I love their first four, and they put on an amazing live show.