My main gripe with the game wasn't the ending, it was spending all the time running around and developing characters in the second game that you only got to use, or not use, for a handful of minutes the entire third game. I know they did the same with Ashley and Lliara in the second, but those characters got to come back for the finale.
Jack, Legion, Miranda, Samara and yes Jacob (man is the only human professional aside from shepard) I used quite a bit for their powers/and or dialogue insights into the game.