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.
My favorite game of all time is Star control 2, and this was the closest thing I could imagine to a modern version it.
They simplified some of the planetary resource gathering, ship upgrades and exploration, and I was hoping they would expand on that in the sequels. Unfortunately they did the exact opposite and simplified it even further.