Most competitive games reach an equilibrium stage that’s often called the metagame. An important distinct to note is that while gamers can reach an equilibrium, it is not necessary the solution to the game, rather, the metagame is the solution to what everyone currently understands and know in the game’s player base.
There are also games that do not have an equilibrium. For instance, there is no equilibrium strategy to play in Rock, Paper, Scissors. By comparison, marines and medics is often considered an equilibrium strategy for playing Terran in Starcraft. The player can choose to build purely medics, purely marines, or a mixture of both. Their best decision tends to be to build a mixture. In game theory, this is called the dominant strategy because compared to the alternative strategies, the dominant strategy is always better.
Practically speaking, it is very difficult to design a game that has no equilibria. It is also very difficult to build complex games with an equilibrium in mind. Most games have evolved outside of their creator’s predictions; it’s why games tend to be imbalanced until substantial play testing has occurred. A game designer can try to influence the equilibrium, but it’s unlikely that he’ll predict what ultimately will be done in a competitive environment. The collective gaming community has proven to be far superior in finding the best strategies. Afterall, I doubt that the original designers of Starcraft even considered building supply depots in front of their bunkers.
From a game theory perspective, games that have no equilibrium have no solutions. To an extent, games, in particular, RTS, that do not have very strong equilibrium strategies tend to be casual. The lack of equilibrium strategies make it difficult to win, at least in terms of strategic thinking because there are no “solutions” that can be played by higher skilled players. In other words, there is no hierarchy; no ladder or ranking system because you cannot be better than another player. When strategic play becomes less important, the next most important factor is the player’s performance which is reflexes, mental state, micro, and other factors that can be improved by practice. It may not matter what you play in Rock, Paper, Scissors, but you can at least intimidate him with mind games which I suppose could give you the winning edge.
There is another form of competitive gaming that should be noted. There are games that are won by strategies which we can discuss using the tools of game theory, however, there are also games that rely on performance. Games like Soccer and Counter-Strike have some degrees of metagame, but compared to a RTS, they tend to be more dependent on player performance (ie. how fast you can headshot someone with the AK as opposed to choosing between building more troops versus expanding). Competitive gaming exists outside of game theory solutions, but those tend to be games of performance rather than strategy.