According to Nick Clifford, who’s in Product Marketing at Bioware: Bioware didn’t do a good job with making it easy for a new player of Mass Effect 2 to understand what was going on. For the most part really the game assumed that you had played the original and so if you started up straight into Mass Effect 2 then you would be in for a bit of a confusing time at first.
Anyway, apparently Bioware is going to make it a lot easier for the new player in Mass Effect 3. Characters will act differently towards Shepard depending on whether you load up a previous save game or whether you start a new one from scratch, there will be a “story so far” type of narrative within the game and there is the new companion for Commander Shepard (James Vega) who Commander Shepard can fill in on the plot. You can hear more here from IGN.
All in all Bioware plans to make the game a good experience for both the old and new fans alike. Good on them.
I would just like to add here though, I thoroughly and completely recommend that if you ever consider getting into Mass Effect that you start from the first one. You don’t have to do what I did and do EVERYTHING (twice… in both games…) but the more you do the richer the back-story becomes. The carrying over of save files just makes each subsequent game all the better as you meet old characters and hear about old situations. Basically, it makes the whole experience just so much better.
Trust me on that.