It's been six years since we lost the greatest voice of our generation. Or perhaps any generation, for that matter. Despite knowing how this tale tragically ends, it's hard not to hope for a happy ending while watching Kevin Macdonald's brilliant but heartbreaking documentary 'Whitney.' The film is equal parts entertaining and devastating, mapping Whitney Houston's meteoric rise to fame, her tumultuous relationship with Bobby Brown, her continual battles with drug addiction, and the tragic downfall which led to her untimely death in a Beverly Hills Hotel bathtub at the...