In the recent years, I've played mostly Magic: the Gathering (drafts) and Civilization V. In MtG, there's plenty of card combinations to try out. You can theoretize about efficiency of particular build in various scenarios, but it's best (and very fun) to verify your theoretical creation in real games. Similarly for Civ V - the game has enough depth built into it that you can approach it very differently (I have around 600 hours logged into it and I'm only now feeling like I've explored most that there is to this game). People who are more meticulous or more detail oriented can probably put a couple thousands hours into the game though, and try out smaller subvariants of strategies that I don't bother trying out.