The plot is, take it or leave it, describable in a single sentence: "Human orphan is raised by Santa's Elves and becomes a manchild unaware of human customs when returning to the human world". It's remarkable how a single joke can be recycled about 500 times, eventually amounting to a feature-length film; sure, Will Ferrell makes for an adorable manchild, but his shtick of being a near-retarded flat-character gets annoying even before the prologue's fully ended. The girl he semi-meets and manages to semi-win over, is evenly flat-charactered, and barely goes out of her way to speak in a non-monotone voice - again part of the act, but dragged out for way too long.
Cinematographically, the film's no good either, for the most part. Seeing as to how the CGI and set decoration in the 'Elven Village' are undescribably bad and the camerawork oftentimes lacks depth of field, the movie has to redeem itself in Christmas lights. We're talking 2003: I've seen better cinematography in films from the 1940s.
Summed up, "Elf" lacks depth. It's one big play on the concept of "manchild in NYC", with the addition of some half-assed critique about corporate America: no good.