Almost any of the Michael Crichton book/movies would fit that statement. In the much more rare category of movies that are better than books, there are few examples, Chocolat is one I think of very quickly (Johnny Depp doing an Irish accent and a much happier ending than the book). Die Hard is another (the book was by Roderick Thorpe and was called Nothing Lasts Forever - you didn't know that, did you?).
In terms of recent teen writings translated to movies, the Harry Potter movies were all good, however they left a lot out, which is inevitable. Twilight - ick - was relatively well translated. I felt the movies were as equally as terrible as the books. The new hotness in tween reading is the Hunger Games series by Suzanne Collins. I have read the first two of the three book series. In my opinion they are better written and more interesting than the Twilight books, in fact, there is almost no comparison. The reason I mention them together is because they are mentioned together often in the media. Really, the similarity ends in that they both have teen female leads. Bella is a lovestruck teen who realizes that she cannot live without her sparkly (seriously? ugh.) vampire boyfriend. Katniss Everdeen, the Hunger Games lead, is a teen who illegally hunts in the woods near her home to provide for her mother and younger sister, and then volunteers to participate in a tournament where kids fight each other to the death in order to save her sister: badass and awesome.
The movie is a faithful adaptation of the book, which I really enjoyed - it was a fast read, and really well done. The movie is also really well done. If you are not already aware of the plot - let me try to quickly summarize it. Set in the future where North America has been divided into 12 districts, and ruled by a ruthless Capitol - each year two teens between 12 and 18 are selected from each of the districts to fight to the death in a televised event called the Hunger Games, which are used by the Capitol to remind the districts of their complete control. Katniss, the heroine of the story - volunteers in place of her younger sister, and goes into the games. That's a brief summary - the book (which I recommend) goes into more detail of the how and why and backstory.
The movie is directed by Gary Ross, who had previously done mainly writing. The problem with reading the book first is that you always have pre-pictured in your head how all the characters should look. I have to say that transition was well done in this instance. Jennifer Lawrence, who is already Oscar nominated for Winter's Bone, does an excellent job with Katniss. She has to carry this movie, and be equal parts strong and vunerable, which she pulls off. Much has been made of the 'love triangle' between Katniss and Gale, her hunting partner played by Liam Hemsworth, and Peeta, her co-tribute entry into the Hunger Games and played by Josh Hutcherson. Hemsworth is decent, there's not enough of him in this movie to really judge what he's capable of, besides, the fact that he's dating Miley Cyrus makes me judge him poorly. Hutcherson, who was just in Journey 2, does a decent job with Peeta. Some of the other standouts are Elizabeth Banks as Effie Trinkit (I keep being surprised by Banks in movies - she's always better than I expect), Woody Harrelson in a distractingly terrible wig as mentor Haymitch, the return of Wes Bently (American Beauty's plastic bag boy) as Seneca Crane, the fantastic Stanley Tucci as Ceaser Flickman (expanded in the movie?), and Donald Sutherland as Donald Sutherland...I mean, President Snow.
8 out of 10.
I'm taking points away for Wes Bently's facial hair....gaining points for the intense action...losing points for the marketing nonsense of pushing the 'love triangle' nonsense. The story is much better than that! Gaining points for making me think at the end, "wow, I want to see the second one right now."
Bonus Video: a trailer for the Muppets spoofing the Hunger Games trailer! (If you haven't seen it, you should- it's big time fun!)