In Spielberg's Jurassic Park, Lex and Tim are the perfect mix of vulnerable and sympathetic. You root for them to make it out alive and well. It's perfect for a disaster story.
In Crichton's novel, Lex is vulnerable and bothersome. She is an extreme liability to Grant and Tim and, when danger nears, her vulnerability is annoying. You feel bad that you want a T-Rex to eat a child, but, seriously, she just needs to shut the fuck up.
In War of the Worlds, Spielberg's child actors land firmly in the Crichton camp.
Besides that, the story is meh with none of the mystery and paranoia of the Orson Welles radio version, the Tripods are unoriginal, the lighting is inexplicably washed out, but -
Tom Cruise is a Goddamn movie star.