One was more of a "hardcore" RPG than the other games which definitely leaned more toward the action genre. If you can get ME1 on PC for cheap, I would try it out. That game is really driven by the story, so you might not even mind the outdated mechanics and quirks. If anything you could play through the first few hours on the Citadel and learn about the different races and get up to speed on what brought the human race there to begin with. There are some really amazing concepts about the story that you might miss if you skip it altogether. If you do just read up on it, I would try to find the most thorough synopsis that you can.