Here is video proof that I Am Legend would have been a lot better with practical monsters. Watch this makeup test for an I Am Legend plague zombie, that the film-makers passed over in favor of a CG army.
Steve Johnson, whose behind the scenes work on The Abyss and in Ang Lee's Hulk we've featured before, is releasing all of his FX secrets via his youtube channel. This particular bit of work was for Francis Lawrence's I Am Legend, starring Will Smith. Sadly, the director didn't think he could get the emotional performances he needed out of the practical monsters, so he went with the all-CG zombie instead. (Also they probably couldn't make that horrible stretchy jaw) Ah well.
For more information on Johnson's works (and to check out some of his fantastic Rubber Rules DVDs) head over to Eon Entertainment.