If you're into sci-fi RPG, then you must own this game.
Which leads me to the development of the characters. To the guys at BioWare, I commend you. Games like this one usually don't get so deep into the supporting characters. Each member of the crew has his or her own background and personality. How well you get to know them is up to you. You can even choose to pursue a romantic relationship with one (or more) of them if you want. Once again, the choice is yours.
The voice acting is pretty on-point. I mean, it should be when you have the voices of Keith David and Seth Green among others (not so much the latter, no disrespect to Mr. Green). The musical score is fitting for the situation, and some of it is almost movie-esque. The gameplay flows smoothly from combat to casual, probably because of the accessibility and ease of use of your weapons. Simply equip, point, pull, and repeat steps two and three as needed. Sure the weapons are basic, but they get the job done. If you want, you might not even have to use your guns. Depending on the character class you choose at the beginning, you might have biotic, "force-esque" abilities such as push or lift that grow stronger as you progress. So you either perforate your enemies or go Jedi on them, or both (sorry, lightsaber not included).
To wrap up my (lengthy) review of Mass Effect, it's smooth, immersive, and has great replay value. Definitely worth every penny.