I think U2 were my first love, certainly the first band I became super passionate about. I've been a fan since 2002 and been on and off with them, but I was super into them around 2009. Radiohead are the other band that I am absolutely in love with and probably my favorite band these days. I got into them around 2006 or so. They've had a remarkable career and have been more consistent musically IMO, granted they have fewer albums than U2. That said, other than Pablo Honey which I like about half of, I generally like to love every one of their records. I eagerly anticipate every new album from them too. I do belong to some Radiohead forums as they have a very active online fanbase, albeit Radiohead fans might look down on U2, but I guess it goes both ways.
At the end of the day, these two bands are tremendously important to me and my development. They opened the doors for discovering so much music in my life. Of course I love other bands dearly, such as Blur, The Cure, The Pixies and New Order to name a few, but U2 and Radiohead are especially significant.