Warning: I am intentionally focusing on the negative aspects of the game to give voice to some criticisms that may not be adequately addressed. It's also a little erratic. I need to go do work and I've already spent the last hour or two thinking collecting my thoughts.
ME3 never engaged me and maybe it's my fault. Having spent almost 70 hours on the series before abandoning 10 or 15 hours from the end I feel the need to develop some kind of justification for stated abandonment and some kind of cogent understanding of my brief relationship the series.
-2&3 feel like a rewrite of 1.
ME1: Fly around the galaxy, find your team, form bonds with them and destroy a reaper.
ME2+3: Fly around the galaxy, find your team, form bonds with them and destroy the reapers.
Playing the series in immediate succession, some of the character changes feel abrupt and unwarranted.L iara and Grunt's in particular. Liara, from damsel in distress whose interests lie in science and archeology to information agent with a penchant for intimidation. Grunt loses any and all qualities that previously differentiated him from any other Krogan. He is Grunt only because I am told he is.
The manner in which characters are brought back is frustrating. As we progress through the plot a previously important and apparently no longer relevant character is revealed as a pivotal aspect of the plot point and invited back to the ship. By chance. As a representative of one of billions of their species. Billions. Off the top of my head Ashley, Legion and Garrus are all brought back in this contrived manner. What it did for me was limit the scope of the universe. You can tell me that the universe is huge, but I can't really believe it when I keep running into the same 12 people.
In the end, with some exceptions, I found it difficult to sustain any kind of meaningful vested interest in the universe. When Mordin, the Salarian scientist and a character I considered one of my favourites exploded I laughed out loud. Tone equivalent films work because the melodrama is restricted to its 120 or so minute running time. The premise alone of the companion missions are flimsy - "hey man i know the world's ending and i'm a but like **** my son is like walking down the wrong path and i think we better take the most impressive ship in the galaxy and you know what **** you." But they also backfired because I felt satiated by their family oriented melodrama.
As a high-concept vehicle to explore some interesting sci-fi and even philosophical ideas I did appreciate Mass Effect but I stopped feeling engaged with its low-concept aim. Character development and personal investment were lost on me. As for gameplay I found ME3 the dryest. There is no vehicular play and no puzzles to break up shooting.