There is no singular "most important thing" that applies to every game. Games can encompass, or focus, on many different experiences. Attempting to narrowly define what a game should or should not bring to the table is a futile endeavor.
One of the most important experiences of my gaming life was ICO. The game-play is nothing special, yet the game itself absorbed me completely. Perhaps for the first time, the emotions of the protagonist were MY emotions, just as with a great novel or play. I would not trade that.
That's why variety in gaming is very important to me and why the whole "game-play is the most important" argument is meaningless.








