My personal rankings:
1. Achtung Baby (Best. Album. Ever.)
2. The Joshua Tree (where the term "typical sounding U2" originates despite the fact that each era has such a different sound
3. The Bomb - Personally I've never understood the hate for this, I agree with the fact that it doesn't flow like JT and AB but individual songs are great enough to make up for it, if they had released it with Mercy instead of AMAAW, it'd be even better.
4. War - The raw U2, love the sounds, the lyrics, the themes, very different time for them though
5. Boy - Stunning debut as someone said earlier, the clarity and purpose in their lyrics wasn't quite masterwork but they were getting there...Stories for Boys
6. Pop - Love many of the songs, but sometimes the weird production is too much.
7. ATYCLB - The first half of this album is amazing, the rest is decent but not enough to put it that high up. Peace on Earth and Kite though are great under-rated songs.
8. The Unforgettable Fire - MLK, Pride, and Bad are 3 of the best songs ever, but the album is short and without flow or much of a theme
9. Zooropa - A bit too bizarre for its own good but Stay is so amazing, its worth listening to the whole thing just for that, I am a big fan of the middle of the album though Numb - Daddy's gonna Pay
10. October - Great songs, love it, just nothing to lift it up to the top tier.
I don't really count R&H as a studio album, I like a lot fo what's there but it's new material amalgamated into a soundtrack.
Passengers is an entertaining side project, but doesn't bear the name U2 for a reason haha.