Fairly disappointed in the Mamma Mia movie, even given my super-low expectations. A few thoughts on why it failed so miserably:
1. General incompetence: in singing, in choreography (holy shit the choreography -- did the choreographer basically just tell them all to go figure something out in their bedroom and then they'd rehearse it with a chorus line?), in cinematography (y'know what'll make this number pop? SPINNING THE CAMERA!), in editing (which seems to have been randomized a la the last minute of this klassik Youtube mash).
2. General incompetence: in singing. Did I mention the singing? And how bad it was?
3. Anyway. TOO MANY EFFING CLOSE-UPS. The entire film has a weirdly claustrophobic feeling, even for a flick that takes place on a small Greek island. Also, it gives us way too much intimacy with the characters, and has no sense of when to let the film pull back and let in the full (WIDE WIDE WIDE angle) scope of its improbable choruses. See: Pennies from Heaven, The Young Girls of Rochefort, and even that one doesn't quite know what to do with a slightly-too-old Gene Kelly. There's an unflattering telephoto flatness that pervades the whole thing, smooshing everyone together in space instead of giving us a sense of a big stage musical breaking out in the midst of an actually quite sad story.
4. Along those lines, the broad strokes of the story are pretty genius, the pop getting mixed up in the melodrama like the peanut butter chocolate goodness of a classic ABBA tune. But the film (maybe the show) itself doesn't really seem to fully understand how perfect the story is for the music, and falls back way too hard on camp, undercutting much of the music's sadness and occasional black humor. Most egregious example is when they reverse the meaning of "When All Is Said and Done," one of the best songs about D-I-V-O-R-C-E evah, to be a kind of "we're not too old to be together!" thing. NO!!!! It completely destroys the weirdly fragile charm of the song, in which a divorced couple reminisce with bittersweet fondness over the time they've had together, admitting they can still see each other, and other people, but just don't work together any more. So much beauty wasted. Minor offenses: changing the gender of "Does Your Mother Know" takes away much of the uneasy, sorta slimy appeal of that one, and "Lay All Your Love on Me" is demolished in context for some reason. Haven't figured out quite why, but again the gender reversal isn't doing any favors.
5. Movie's having a lot more fun than we are. Most present in the epilogue, in which Meryl Streep and co. finish a refrain of "Mamma Mia" and she kind of exasperatedly shouts out "DO YOU WANT ANOTHER ONE?!" with an odd snarl, leading into "Waterloo." It's like the whole cast is tired, as though this was a real-time documentary and we're on the final number. The whole film has an air of forced smiles to it, everyone realizing in the thick of production that what sounded like fun on paper, and looked like fun on stage, was turning out to be more of a chore as a film.
Seriously, no forgiving what they did to "When All Is Said and Done." The movie is basically to ABBA's music what "Glee" was to "Don't Stop Believin'" -- an oddly formal exercise in frivolity that seems to understand intellectually the appeal of its source without being able to actually convey it. Which, of course, is one reason why ABBA is brilliant.