The Lovers: Commander Shepard and a whole mess of partners
"Hey, Shepard? Whatever happens down there, I just wanted to say..."
Whether you played as a male or female Commander Shepard, there were more than a handful of worthwhile romantic paths your character could take through the course of the Mass Effect games. While the first game essentially paired you off with a token love interest with only one other, "neutral" option, Mass Effect 2 introduced characters whose romantic status could evolve over the course of multiple games.
Mass Effect 3 had a whopping 11 different options depending on various elements, but they were all intertwined with your decisions through the game, and in games before it. It means a lot to have such a bredth of possibility and accountability for the actions you take.