Megan McArdle:
FDR lived in a different era. His speeches come across so well today precisely because they were designed largely to be read; Obama is making speeches for an era when most people get their news from television, and so naturally, his speeches read flat and uninteresting. FDR's speech delivery, by contrast, was surprisingly poor for an audience used to taking in most of its news in audio or video.
FDR would do just fine on video: