Yesterday I finished Mass Effect for the first time, and as soon as I had done that I just had to start at the beginning again. I started a new game with the same character (the default) so now I can hopefully get the 50th and 60th level achievements.
To get 100% on this game I would have to finish the game at least three times though… I’ll have to see if I think it’s worth it. I think the game is really good, so it’s not impossible that I will try to get 100%.
Now I am reading up on the Mass Effect wiki to try and get most of the missions and achievements in the game.