I use Facebook to post pictures of my vacations for my family, and get updates on my nieces and nephews since I moved from Houston, TX to NYC 5 years ago.
Until someone replaces that aspect in a way that works while still enabling my family to do their memes and quizzes, and all that crap I avoid, there will be no "rival". I HATE Facebook, but I can't get rid of it without losing access to my family.