I'd say この映画は長いです When we use the word 長い refering to a film, we understand we are refering to the time it takes. I hope this helps!!

In Japanese, the same word is used for time as is used for length or distance. That word is 長い (ながい), so you might say: この映画は長いです。(this movie is long) OR　 この映画は時間がたくさん掛かりました (this movie took a lot of time) The first one is more likely, however.