Busted always win for me. I really liked McFly in their heyday but Busted were the original and best. They also remain, to this day, highly underrated. As musicjukebox123 said in his/her (excellent) post, they were very influential and you can still see that influence in many boybands today. They pretty much ripped up the rulebook for the nineties model of boybands, but even though their songs were rock-influenced, they were never anything but pure, joyful pop.
Although it's a shame they split up when they still had a lot to give, in a way it was very savvy of them to do so as they left a pretty much flawless discography in their wake.