One thing I respected about No Line on the Horizon was that it really sounded like it was an album they made for themselves, without trying to figure out what their audience wanted to hear.
What it isn't though is a good album that I'll ever listen to again. Although I agree with the OP that U2 has been pretty boring for quite some time, I did enjoy Achtung Baby and Zooropa so I'd say they were viable for at least the first half of the 90s, Zooropa in particular is highly underrated IMO.
In any case, the new generation of bands like Radiohead and Arcade Fire have clearly taken over from them in the inspiration department.