An ingenious game

First things first: It is highly recommended to have played only the first two parts on the same platform (PC, Xbox, PS3), because the story is extremely large and on the decisions you adapt Meet, or changed. The decisions of the first parts can be imported in the next, which can make a huge difference (for example, whether an entire alien race are your allies, or they have been completely wiped out and no longer appear to be)

In my opinion, Mass Effect 3 is the best so far combination of Shooter and RPG. The gameplay is fun and the character creation, and the development is varied. In addition to the long main story, there are many smaller search and collection drives, and really well-written side missions. All in all I have needed 41 hours to all side missions to do except for one, to find about 80% of all collectibles and play through the main story.

The free update to Mass Effect 3 is also recommended, as so take your own decisions in the third part of more influence and the final game sequence is extended.

I've played it without the first two parts and it was doable, but I have, because I wanted to better understand the story, often read summaries and explanations of the first two parts. Whether with or without the first two titles, I can highly recommend ME3.