RadioLab has a recent podcast on games, specifically why they have such a hold on us.
There's a great segment on checkers which talks about how two master players in the 19th century played 30 or so games together as part of a competition. Over 20 of them were the exact same game, ending in a draw. So this game that they played over and over again must have been the best game of checkers they could have played, otherwise they would have changed their moves somehow. Since they were the best checkers players at the time, that means that this game they played was the best checkers game ever. That's it, no better checkers games can be played, ever. Checkers was won. From a certain perspective, after that game there was no longer any reason to play checkers.
Checkers, for this reason, is a dead game. For someone who studies the game, there will be no more surprises. It has nothing more to offer. Chess, on the other hand, is very much alive. The sheer number of possible moves is so vast that it would take an incomprehensibly long time to play every single possible game of chess. The number of possible chess games is, however, finite, and there is some single set of moves, a single strategy, that is more powerful than all others. It's only a matter of time before we find it.
In fact, any game that doesn't contain any randomness will one day, like Checkers, be solved. Randomness, added to a game by dice or by a deck of cards, for example, adds a lot of time to a games lifespan. But randomness only delays the inevitable, for sooner or later someone will figure out the probabilities of every possible outcome of the dice or cards or whatever, and will craft a winning strategy accordingly.
Consider Risk. It's a game that relies a lot on randomness (and starting positions), but there is certainly a winning strategy that accounts for the possibility of each different outcome. The dice are factored into the strategy and thus become largely irrelevant. Thus, a player with the perfect strategy will nearly always win, despite the randomness involved. Is Risk a game that is still alive or is it dead? Once that perfect strategy is found, I would say that it is dead, since the outcome of the game is pretty much determined before the game starts.
My games can never die. They are continually being revitalized by new content created by the players. It is impossible to craft the perfect strategy for Thief or Dog Eared Superhero because so much depends on the subjective decisions made by the other players. Playing Thief, you may think you have a great strategy to defeat all the most difficult obstacles and grab all the loot. But the other players can and will create a new card that foils your plans and puts you back to square one. In Dog Eared Superhero, you might create a series of cards that the rest of the players love and will vote for, but there is nothing you can do if another player creates cards that the other players love even more, with the result that the chosen cards completely changes the direction of the character's development, away from your original plan. These games can be played hundreds of times by the same group of people and there will always be new content leading to new situations and new challenges. Each game is unique and alive.