Between Robin Hood: Prince of Thieves, JFK, and The Bodyguard (the latter in 1992), the top of the '90s were basically Kevin Costner's world, and we were just living in it. Straddling the worlds between action, drama, and romance, he played smart in defining himself as an undefinable actor. But above all, he carried Whitney Houston offstage, making "I Will Always Love You" the most important song of all school dances.