Mass Effect means a lot to me as well. You can hear most of my opinion's about it on the podcast Julian mentioned, but it was one of the most important games of this console generation in my opinion.
The fiction is incredibly deep, and fleshed out. The characters are some of my favorite in all of gaming. The games themselves all provided something memorable, and long lasting that makes me want to play each one over again, which usually isn't the case. I actually went out and bought Novels and Comics based on the fiction because I enjoy it so much.
People can complain and nitpick on things like the ME3 ending, or its sacrifice of RPG gameplay for more Shooter-style gameplay, but in the end the series stands as one of the industries best I feel. A lot of that does come from personal investment of course, so people who aren't into story or characters as much may not feel as attatched as i do, but I still feel everyone should try the series because they might find something to enjoy.