The game tic-tac-toe is something only very young children enjoy. Before long one learns that one can always avoid losing and if both players discover this, then you have only drawn games. But via Cory Doctorow I learn of a variation called Ultimate Tic-Tac-Toe that is extremely easy to learn but promises a quantum leap in the strategy required as well as in challenge and fun.
I suspect that over time, there may be an optimal strategy that will be discovered but the number of possible variations might be so large that most people will be unaware of it.
If you go the end of the article, you will read about variations on the game and (of course) there are apps if you want to play online.