I always like to hypothesize about The Essential U2...but it likely would have next to no deep cuts. Let's face it, the amount of memorable songs/hits that they've had through the years would manage to fill up both discs pretty damn quick.
At most, you could cut "When Love Comes To Town" from the package among The Best of 1980-1990 tracks, but you would likely have to add in "Gloria"...so the 80s is already represented by over an hour of material which means there's a whopping 100 minutes left for the rest of their discography.
All four singles from All That You Can't Leave Behind would have to be there...so now you've got a full disc's worth.
Achtung Baby would have to be represented by the four tracks from The Best of 1990-2000 at the least. "Stay" would need to be there..."Vertigo/City/Sometimes" would all need to be there. That's close to half a disc right there.
"Discotheque", "Miss Sarejevo", "Every Breaking Wave" and "Moment of Surrender" would practically all be guaranteed to make an appearance (you figure every album will get at least one bit of representation). "Hold Me, Thrill Me, Kiss Me, Kill Me" is one of their biggest hits from 1990-onward, so it would practically have to be there even if people forget about it from time to time.