This game made me feel like the captain of a space ship. There was nothing like it at the time it was released, and even now I have not experienced any other game making me feel this way. I loved Fallout 3 too, but Mass Effect had something special. It was so well crafted, I listened to every dialogue of every NPC. The characters are so memorable with amazing voice acting. The Citadel is the best city in video games, felt really alive. Most sidequests add to the story instead of just padding the gameplay time.
After playing the game, I wondered how Star Wars (movies) sucked so badly, when a video game could create a much more interesting sci-fi world and story.
Unfortunately Bioware is no longer the same company.
Look up game mechanics and progression to see what style of char you want. 3rd person cover shooter w classes, squad mechanics, and RPG elements.
Avoid story and character spoilers as best you can.
Your save files carry over through the three games which was unique at the time and really ties the games together in a meaningful way.
Still pretty unique, isn’t it? I remembered this feature a couple days ago, and couldn’t think of another example.