One angle for this intriguing comparison is the angle of credibility; what's the instrumentation, what are the lyrics, how complex is each song's (or album's) texture, and how do these elements measure up to the high standards that U2 fans have for U2's music?
WARNING: OPINIONS TO FOLLOW

The Zooropa album flexes creative muscles with instrumentation (Zooropa, Babyface, Lemon, Daddy's come to mind), inscrutable/provocative lyrics (Zooropa again, Numb, Lemon, Stay, The First Time, The Wanderer), and texture (The title track and Lemon are now 3 for 3). So we have 2 standout songs, Zooropa and Lemon, and many others that are strong in one area. There are a few songs that don't make any of the cuts: Some Days . . . and Dirty Day. Are there more than 2 songs that I like on Zooropa? Absolutely. Would I expect more than 2 home runs on a U2 album? Yes, especially given JT and AB being in the back catalogue at this point in U2's career. Babyface creeps me out a little bit - the whole pornography thing . . .
So over to Pop. The instrumentation throws us for a loop on many tracks, because we're wondering where the "Edge guitar" sound is. Discotheque, Mofo, If God . . ., Staring at the Sun, Gone, Please, Velvet Dress, and Wake Up . . . especially push boundaries/defy expectations. Lyrically, Do You Feel Loved, Mofo, If God, Playboy Mansion, Please, and Wake Up . . . are standouts, either levelling with us about real feelings of love, loss, and anger, or using creative images to express these feelings. The songs on Pop exhibit a variety of textures - the all-out techno rave of Mofo, the almost unplugged feel of If God . . ., and the buildup in Please are good examples. This gives us 3 standout tracks: Mofo, If God will Send his Angels, and Please. The instrumentation on Gone makes it a standout for many listeners, myself included. Miami is a kind of fun song but is not at the top of any of my lists. I think Last Night on Earth is "mysterious and cool," in the words of another forum poster, but I don't think it's as strong as some other pieces. What really makes Pop's case for me is how many songs are pushing the envelope or stand out in at least one category. I think it's worth noting that many pieces on Zooropa are lyrically significant but not as strong musically. Bring on the counterarguments, Zooropa fans!
These are my more-than two cents; I guess I like when the lyrics, instrumentation, and texture in a piece all come together, and that happens for me more often on Pop than on Zooropa. Peace.
