A potential masterpiece somewhat let down by poor direction, unconsistent art direction and bad gameplay and level desig
There are four main problems in this game: direction, art direction, coherence and level design.
Direction: while the game is visually one of the most impressive games to date, direction (both of the cutscenes and the overall pace of the game) lacks punch and sometimes is simply a bit slow. While comparing ME to GOW or MGS might be inappropriate due to the more fps nature of the latter twos, there are simply too many well directed games out there, and a game like ME, with its vision and scope, should have deserved better.
Art direction: Art direction is a mixed bag, being incredibly good into conveying some Sid Meadesque kind of science fiction, but failing to express the grandiosity of the latter and lacking variety. Whenever I play ME I think of THX 1138, while I would have loved to see some Blade Runner and Star Wars in it. Everything looks too shiny and too polished, and you somehow get bored quite soon by environments that look very similar to one another. There are of course some exceptions: characters are probably the most realistic and varied in a videogame (maybe except Crysis) and the alien races are convincing and well done. Yet, even with characters, there's always this strange idea of future vision, where everybody (civilians, aliens) wear this tight "uniform like" dresses (sober and without any style or character) and live in clean white plastic boxes that came out of a 1980s office furniture company.
Level Design: this lack of grandeur (or vision) is even more evident in level design. The Citadel is a convoluted and devoid set which looks pretty small compared to the general idea such place should convey, and compared to urban settings in other games (let alone GTAIV) is simply a let down. For comparison, the interior of the Normandy (your small ship) should be fifty times smaller, and sadly isn't. Speaking of which, your spaceship suffers from some strange scale effect, and somewhat the interior looks and actually is larger and bigger than the exterior. The interior design of the ship is all but functional as well, and you keep asking yourself which kind of engineer drafted such a uncoherent bunch of interior spaces. External environments show again all the problems this game suffers: instead of freeroaming places you'll end up with quite linear levels that lacks variety and seem small and confined.
At the same time the game lacks coherence and realism. Examples are everywhere: In the game you'll end up in the council room facing the most powerfull political organization in the known world and not only you won't wear a uniform but you'll be fully armed and equipped instead, ready to kill the councilors if you really wanted. The Normandy looks more like a Las Vegas suite than a spaceship, with lots of wasted space, duplicated rooms (why would I need a room for the galactic map and one of the tactical screening?) flimsy bulkheads and basically no engeneering. The problem is that all this quirks translate in bad gameplay as well and you'll end up running along the levels just to talk with a few characters or perform otherwise simple actions. Combat is a bit uninspiring and uniform as well, having finished a lot of close combat missions only using a sniper rifle.
In the end, this is definitely a good game, something that could have been a masterpiece but is let down by some aspects. And while this issues might have been irrelevant in any other game, given the high overall quality of this title they simply stand out and ruin the overall experience.