Very fun, but also quite easy
Positives:
The game looks amazing. It genuinely looks like a playable movie. The makers put in some strange effects, such as film grain and motion blur, to add to the realism. These really did not add much to the overall beauty, but if you like them you can use them. I personally only use the film grain.
The mechanics are up to par. There were a few instances where the camera would mess up, especially in the Mako, but these were few and far between. The gameplay itself was enjoyable and works well!
The story and how it is shown are the really great pieces to this game. Their choice system in conversations is spot on. With this, it is amazing how well each option has its own individual vocal response and most of the time its own individual facial expression. This really is a step forward for story in games. Reading about each alien race and other information the game provides in the codex, added a tremendous amount of depth to the story. You could make it through the entire game and not read one of these little tomes of information, but you gain so much in reading these, why not!
Another great addition is the Galaxy Map and its different areas to explore. It felt really great going into a new star system and exploring the different planets and reading about them. This really added some great elements to the game, and really bolstered this game as a new mark in storytelling.
Negatives:
The game seemed just a touch easy. I usually only play games on their default difficulty level, but I decided to play this game again a couple times on the unlocked difficulties. Even at these higher challenge levels, the game was a breeze. This may be because the game itself gives the player far to many outstanding weapons and tools. Practically in every area you explore there are unlockable containers, which usually contain 1-3 items, which seem to increase in potency with your characters level. By the time you get to levels 51-60, these "treasure chests" become more of a chore than a reward. I've probably seen around 150 High Explosive Rounds, and when you can only carry 150 items you end up just destroying the items you find. Oh well, for the amount of writing I have here, this really is just a minor fault, which is my opinion.
Mako. period. The Mako is a vehicle that is used in various parts of the main storyline, and used to explore worlds during the side quests. There were very nice moments with the Mako, which broke up the game, and added some different elements to the gameplay. I constantly was frustrated by the Mako though. Especially dealing with the turret. I felt the Mako may have been thrown into the game during the last stages of planning, and could have been much better.
That's it! If you haven't played Mass Effect, go out and play it. It's only around $20 right now, and it is definitely a great 360 game. I am looking forward to ME2!