I love 4X games. I’ve tried other strategy game genres, but frankly, they don’t stick if they’re not first and foremost 4X games—at the heart of it, it must be about exploring, expanding, exploiting, and yes, exterminating.
I suspect that the first 4X game most people played was some entry in the Civilization franchise—though certainly, a select few played precursors dating back to text-based games in the 1970s.
But for me, the title that kicked off my obsession was Master of Orion II (MOO2)—a game that has you develop and build up planets across a simple galaxy map, researching speculative future technologies, and ultimately wiping out your opponents and claiming dominion over the known universe. (There are other victory conditions too, but that one is the most fun.)