You already saw the other performances at last night's Billboard Music Awards, but this one just might be the most important of them all. Both John Legend and Jordin Sparks honored the late Whitney Houston with a pair of covers of two of her biggest hits, "The Greatest Love of All" and "I Will Always Love You," respectively. And after they hit the stage, Bobbi Kristina takes the stage to thank everyone for all the love and support they have shown the Houston family since Whitney's death this past February.