The only way to say that Russell played the best game ever is to overlook a crucial part of the game: how the winner is decided. The game includes the final vote, so if you play in such a way as to ensure that you will not win that vote, then your game as a whole is flawed.
You might say that the people on the jury should vote based on who played the best in terms of getting to the final 3, rather than on who they like, or who made deals with, or who they find, you know, not evil incarnate. But that amounts to saying that they should play a different game; Russell might be good at that one, but he wasn't good at this one. And the fact of the matter is that Russell should know how people on the jury typically vote, and should have played accordingly.
Analogously, you might think that soccer games shouldn't be decided by penalty kicks, since that captures only a small part of the what the game is about, and should instead be decided by continuing overtime periods (maybe sudden death, going to 7 v 7 at some point, etc.). But the game as it actually exists includes penalty kicks, and a team that went into the World Cup without practicing for PKs could not be said to have prepared the best game. And it would be no defense if a team lost on PKs, but protested that they shouldn't be part of the game, since just like Russell, they knew that they ARE a part of the game and planned accordingly.
Only difference is that soccer games won't necessarily be decided by PKs, whereas Survivor will necessarily be decided by jury vote, so Russell's failure to play with an eye on that necessarily dooms his game.