I would be willing to bet that "I Will Always Love You" is Whitney's most played AC song, before or after her death. It's pretty much a staple, even though it is rather slow and is a ballad. Was a huge hit and the song she was best known for. She had some pretty good uptempo songs from the 80s, like "I Wanna Dance" and "How Will I Know", which aren't heard very much anymore (well, weren't until after her death). I liked her remake of "I'm Every Woman", even. Those seem like great Whitney songs for the AC format. Since she had quite a few slower ballads as hits, but since the AC format doesn't like that kind of stuff (for the most part), the stations are a bit limited as to what they can play by her after they are done paying tribute to her.
I haven't heard a lot of the songs by Whitney mentioned on here played in ages, until she died. "I Have Nothing", "Saving All My Love For You", and "Greatest Love Of All" are other ones that are rarely, if ever heard. I would suppose that they don't really fit the format anymore.
Maybe it was just around here that there seemed to be a MJ resurgance, but I rarely heard any of his music on either of our ACs, but after he died, they started playing 6-7 of his songs shortly after his death. The remaining AC still plays a lot of his music.
I agree that her death is sad. So young and talented. RIP.