I'm going to do a Top 9 because I've never heard Boy or October
1. ACHTUNG BABY(An Epic of a Masterpiece)
2. Joshua Tree(Masterpiece)
3. Pop(Masterpiece)
4. How to Dismantle an Atomic Bomb(Masterpiece?)
5. All that You Can't Leave Behind
6. Zooropa
7 and 8. Unforgettable Fire and War(Tied)
9. Rattle and Hum
Few things: Achtung, Baby! is my absolute favorite album of all time so it kind of gets distance from the pack.
I believe Pop to be very underrated and I'm guessing that many have similar feelings on this site.
I could never really get into War, I guess it just didnt really age well.
The Unforgettable Fire is very artsy and has aged well, but there's a few duds on the album or maybe a lack of really good tracks.
HTDAAB, popular to contary belief, does not sound like the 80s U2. The sound is very much more mature and edgy(in terms of guitar sound). I really put it up there with their masterpieces.
I'll cut my ranting short here.