"Achtung Baby". (Actually, the album after "The Joshua Tree" was "Rattle and Hum", which you may argue was a live album or some such, but it had a lot of original material, too.)

Anyway, I disagree. It was "Pop", but they jumped back with "All That You Can't Leave Behind". BTW, even if you disliked "Achtung Baby" and "Zooropa" (which I didn't), you should totally check out "ATYCLB". It's much less electronica-y, which is bound to be what you disliked about the intermediate three.