Best Actor in a Leading Role...TOM CRUISE
How the hell did Hoffman walk away with the Oscar for this? Yes he was very good, but Cruise's character had much more pivotal and difficult scenes to pull off, which Cruise did perfectly and hence warranted an Oscar nod.
Examples of performances better than Hoffman's in Rain Man include:
De Niro in Awakenings
Di Caprio in Whats Eating Gilbert Grape
Geoffrey Rush in Shine
Shame on the Academy for not recognising the brilliance of Cruise in this film.