An incredible, addictive, dramatic, action-packed marvel!
In essence, Mass Effect has something for everyone... as an RPG lover you will get a rich and dramatic storyline with a lot of choices and some really deep character development, as well as the levelling up factor, ability to choose and customize a character, and a variety of ways to engage in battle. For those who love shooters, there's no end to the action, to the enemies you can use as target practice, and the satisfying range of ways to dispatch them.
Visually, this game is stunning and will leave you breathless when you least expect it; you'll be traversing a rocky planet in your all-terrain space car (the Mako) when you'll crest a hill and see the most spectacular view you've ever laid eyes on.... or pursuing a formidable enemy, and be rocked by the spatial gravity change... yes, as aforementioned by other reviewers, there are some minor flaws such as texture loading and long elevator rides, but these are negligible, and can be almost avoided entirely by the simple act of loading your disc onto your hard drive.
Gameplay-wise, you never get bored; if you are after achievements, you are looking to have to play through at least three times, which seems like a rough hurdle in terms of most games - but in this case you can choose from such a variety of characters and have such a variety of options in the dialogue and choices you make that even after having played through a few times, you will WANT to continue to make new characters; try something different. In terms of difficulty levels, you can start on an easier level to get accustomed to the game, but then move to Hardcore or Insanity for a real challenge. (and bragging rights!)
Battle is intense, and even crazy at times, making for a heart-racing adventure, broken with the calmer times of dialogue and story on the Citadel, or interacting with various characters on other planets. It is an excellent balance of intuitive controls with the potential for more user-interactivity once the player becomes more familiar with the game mechanics, which allows the player to choose their level of challenge, above and beyond the difficulty level.
As an additional bonus, the voice acting is excellent and believable, and over and above the main storyline, there are tons of galaxies, planets and quests to explore at your leisure.
Overall, this is an incredible game in its own rights, and the fact that it is just the beginning of a beautiful series makes it all the more alluring.