I think I'm ready now. Whew, here goes:
1. Joshua Tree
2. War
3. Boy
4. Achtung Baby
5. Songs of Innocence
6. Unforgettable Fire
7. October
8. Rattle & Hum
9. All That You Can't Leave Behind
10. Pop
11. How To Dismantle an Atomic Bomb
12. Zooropa
13. No Line on the Horizon
At first I said SoI was best since ATYCLB -- now it's best since AB and I'm beginning to wonder if it might eventually start to approach (not exceed, but approach) JT in the long run for me. Because like someone said somewhere, "it's a mashup of JT and AB."
I really think it's that good -- although it's still too early to be certain. But I do think it's their strongest overall album in a long, long time.