I can't think of a Crichton movie better than the book. Timeline was one of my favorites by him, but the movie was abysmal.
Sphere was decent, but there's just no way you can truly translate the fear and distrust from the written pages into a two hour film. The cast and crew did a good job trying though.
Speaking of Crichton, if you fans haven't read them I recommend the two published posthumously: Pirate Latitudes and Dragon Teeth. The former feels a bit incomplete, but the latter is fantastic.
One could argue the Lord of the Rings trilogy is better than the books, if you prefer to skip pages upon pages of poetry and lineages, but you'd be wrong. The books are still better, but I can at least entertain the debate.