I feel like this is a cutting-edge philosophy question, like back when the first philosophers dicked about "what is art."
For me, game play is that "thing" that takes something from being a video, picture, art, task, whatever, and brings in some interactive component that includes things like challenge, accomplishment, reward, success, failure, competition, etc.
The most popular games (SEE: NOT VIDEO GAMES) are built on fairly simple game play with basic things like winning/losing, risk/reward, competition.
Looking at a picture is not a game. Looking at a picture with a friend and seeing who can find something first is. Especially if there is pie at the end. Seriously, fuck all you cake-eating pie haters.
