Beware, it's become trendy to give U2 a bunch of unreasonable hate these days, much like Coldplay.
I personally would have ranked them right between "They kick ass!" and "They're ok." I rounded up simply because they're not just some mediocre band.
Unlike most people, I actually like their 90s stuff most out of all of their albums. Pop and Zooropa are really great, perhaps better than Achtung Baby, in my ears. Actually, Pop is my favorite album of theirs. A very different and intense sound on that one. Songs like Mofo and Please can't be beaten.
Nothing wrong with their post 2000 stuff either. No Line on the Horizon is really cool. It really takes something special to make me like 80s music...I guess that's why I barely listen to U2's 80s stuff though. However, I must admit that War is pretty darn good.
I'm rambling. U2 isn't my favorite band, but they're still pretty good.