List the top 5 most-rented films.
film refers to title; most rented refers to MAX(inventory_id)
SELECT T.title FROM ( SELECT T3.title, COUNT(T2.inventory_id) AS num FROM rental AS T1 INNER JOIN inventory AS T2 ON T1.inventory_id = T2.inventory_id INNER JOIN film AS T3 ON T2.film_id = T3.film_id GROUP BY T3.title ) AS T ORDER BY T.num DESC LIMIT 5