I submit this review, being someone who has actually spent some time with Mass Effect. I have beaten the game on Insanity, played through the game four times and I have all achievements except the Ally achievements, which I think are perhaps a little glitched. I only mention all this right off the bat because most bad internet reviews and user reviews of this game have come from people who frankly have not spent the time with the game to truly appreciate or understand it, and may not even be fans of RPG's. And of course, that's okay. We do not all appreciate the same styles of music, art, or even video gaming genres.
Mass Effect has the best story available in this generation of gaming to date. By far, this is the best RPG on a next gen console, with the most incredible facial animations I've seen on a video game. That being said, it does suffer from load times (elevators) & texture pop (Unreal Engine) probably due to the sheer size and scope of the game (Microsoft should have allowed HDD standard & this game could have really benefited from HDD streaming, just like DMC4 did for the PS3).
An average playthrough should take no less than 20 hours assuming you do a few of the side missions and complete the main quest. As this is an RPG first, one should not expect the gameplay mechanic to be as fleshed out as an action game or a standard FPS. Mass Effect is first and foremost an RPG, and as such, its primary focus is on the story and leveling up your character. Arguably, these elements and even graphics may be a greater concern than gameplay in an RPG.
You really need to complete at least 7-8 hours before you begin to understand what a beautiful experience Bioware has put together. The gameplay while not perfect, utilizes great ideas like a Gears of War type of cover system and a third person point of view like RE4, which I personally really like. I find the gameplay to be very well done considering it is an RPG, it has evolved leaps and bounds from the blueprint of this game, one of many GOTY's from Bioware, last gen's Knights of the Old Republic.
I think this game is a masterpiece that can only truly be appreciated by RPG fans. Bioware really crammed an incredible amount of innovative concepts into this RPG. My first playthrough was 36+ hours and I probably only completed about 92% of the game. The sheer size and scope of this western RPG will reward you over and over. This, of course, brings us to replayability.
After you complete the game once, you can begin the quest anew with your leveled up character and all his/her items and continue leveling until you reach Level 60. Or, you can start a new game, completely redesign your character, change gender if you like, and playthrough again as a Renegade or Paragon, whichever you have not done, whatever strikes your fancy. Obviously, being an RPG, there are many character classes to choose from as well, which will drastically affect the way you play the game. Conversations change and different items appear in multiple playthroughs.
Bear in mind, Bioware has a trilogy planned for Mass Effect. The decisions and choices you make in the first game will transfer over to Mass Effect 2, along with your leveled-up character.
This is truly a game that RPG fans, particularly western RPG lovers, should not miss. The classic sci-fi story Bioware spins in this game is much better than most of the sci-fi movies I've seen in the last decade. However, as I have stated many times in this review, this game is not for everyone. Not all gamers will enjoy a 35+ hour game and all the dialogue found in a typical RPG, which I can completely understand. But for those of you who do love RPG's, Bioware has definately created an incredible new IP just for you.