Back then it used to be ME2, but after MELE I'm not so sure anymore. I think that each has strong and weak points, like ME1 has great atmosphere and an epic final level and generally works very well as an introduction but the characters don't quite feel as "human" (in quotes cause obviously they aren't all human) and the dialogues are often stilted and infodumpy; ME2 of course really shines with recruitment and loyalty missions but the main plot is rather underwhelming; and ME3 has some amazing story arcs like the genophage one with emotional conclusions for some of our favorite characters, who by then feel very fleshed out, but of course it being rushed had a negative impact on the final arc and the ending. So I'm just gonna cheat and say that MELE is like one game to me xD Andromeda is of course not as good but I do still like it.