"<font color="purple">I agree with your definition of 'optimal', and that is why I commented that there is no optimal game theory solution, since there will always be a counter-strategy for any given fixed strategy.</font color>"
That may be true if there are three or more players, but not in a heads-up game. In a heads-up poker game, an optimal strategy (as we have defined it) does exist. In fact, the optimal strategy for "preflop holdem" has been calculated (
http://www.archduke.demon.co.uk/simplex/index.html). If this calculation is correct (and I have no reason to think it isn't), then there is no counter-strategy that will beat it.