To begin, let me say I am a huge fan/player of the Mass Effect series. Mass Effect 1 (9/10) and 2 (9/10) were perfectly structured and balanced for that special combination of playability, challenge and storyline - essentially keeping the games fun to play and immersive.
Mass Effect 3, for me, has missed the same combination.
In great part removing the "squad selection" ability from places seriously detracts from the flow of the game. A prime example is the side mission to liberate Omega from Cerberus. This side mission, while starting out somewhat predictably, quickly becomes a series of ridiculous blast-fests for which Shepard is frequently "abandoned" to face almost overwhelming forces alone while not even having the resources necessary to take down some ridiculously overpowered enemies and achieve such a thing as goals.
It seems that somewhere along the way BioWare decided to mix Mass Effect with those duds S.T.A.L.K.E.R and Metro 2033 (both of which I uninstalled)
As far as rating the game, I would give it 9/10 for storyline, 6/10 for playability, Combat system 7/10, Graphics 10/10 (That unreal engine is unreal..!) Immersive quality 7/10, Fun factor 4/10.
All in all a bit of a disappointing follow up to the first two. I do hope that, if there is a Mass Effect 4, Bioware will rethink the approach they took in ME3 and bring the franchise back on the splendid track they set with ME1 and ME2.