Roger Ebert nominated Spielberg for one of TIME magazine’s 100 lists (I’m not sure which exactly) and here gives his explanation as to why. His concluding sentence is particularly good and captures perfectly why I, at least, am such a fan.
“In the history of the last third of 20th century cinema, Spielberg is the most influential figure, for better and worse. In his lesser films he relied too much on shallow stories and special effects for their own sake. (Will anyone treasure The Lost World: Jurassic Park a century from now?) In his best films he tapped into dreams fashioned by our better natures.”