There is a dirty little secret in choice based video games: there is no real choices to be done. This is to be expected as a video game has to be programed and there is no real way to have a player choose a unique path. One game did come close, allowing the player to make relationships while trying to save the universe. Mass Effect from Bioware was a science fiction saga that allowed players to chart their own destiny across the galaxy.
Commander Shepard might be the most important human in 2183. They are being observed to determine if they should be allowed to join Specter, they would be the first human to do so. The enemy are the Reapers, creatures of mechanical origin who threaten the entire universe. Shepard will assemble a crew to discover how best to stop these invaders. The journey will expose the commander to many different species, as well as a traitor closure to home.
The world of Mass Effect is massive. There are so many different alien species that you will encounter and have to deal with. Your choices take the form of actions and dialogue tree. You will have to decide what course of action you will take not only with your enemies, but your cremates as well. You can choose what relationships you will build and which ones you will ignore. They might even take a romantic route. There is no set partner you have to be with, you can choose anyone.
The story and visuals are gorgeous. You will spend a lot of time trying out all the paths before you. Most games treat story as an afterthought, Mass Effect puts it center stage. The best types of worlds are the ones where the player feels they were dropped in halfway through the story. Everything feels real and the choices are not always easy. You can do everything right and someone you care about still might die.
Mass Effect began a world that continued in three games. There is still nothing like the original, as you gain your bearings in this new world. The followup games caused some controversy, but the original does not have that burden. Adventures in space had been done to death, but this game made everything seems new and different. And it gave players real choices.