I never finished the third one. I kinda want to revisit and finish the trilogy sometime. I remember enjoying the RPG elements but looking back on it, it really glorifies the military, you're basically the space CIA if I remember right. You also team up with Garrus, who's a vigilante cop and the Space Fascist in the third one, whose genocidal racism is treated like "haha he's like your racist grampa lol".
And it made sense with the fact that the story is essentially an investigation into Saren and his dealings
With 2 the story starts getting real wobbly, what with forcing you to work with Cerberus because (insert reasons here) and the story basically just being "You need dudes to save everyone"
3 is just gibberish outside of a few particular quests and please don't get me started on the ending