Now I have a vague definition for this. For example I consider Fallout 3 to be an adventure game because you exploration, and, well, create your own adventure. And I see MGS series as falling under action adventure
Now, ME3 is one of my favourite games, and I am confused as to why some people hated the ending.
The hate for the ending comes from the fact Bioware took the lazy way out and gave 3 'locked' choices which in turn are supposed to have multiple endings in themselves (minus control) but in reality there is very little difference between them.