There's a whole universe of possibility out there, and it's been harnessed by Bioware
Mass Effect has more interesting cutscenes, better dialogue, better voice actors, and a better look than ANYTHING that comes before. It's fun, witty, action packed, and at times will actually wrench your heart. One decision you make may affect the rest of the game.
The storyline is pretty straight forward, although you won't care because you'll be immersing yourself in thick waves of information, on races, species, and places you've never seen before. Meanwhile you'll have all of the storylines your partner characters bring, which only expands the scope of this game. ON TOP of that you also have the decisions. Each decision you make will affect you either in a good way or bad. (paragon, renegade) Though I won't ruin the fun, you should also know that there is a point through the game, where your decisions affect EVERYTHING. I cannot tell you how much there is in this game, It's jammed packed full of neat things.
The graphics were really great for their time. The faces look wonderful, and the ships and planets are even better. My only aggravation is the lip sync, which can VERY RARELY be out of sinc with the words, or you just aren't feeling the tone of voice compared to the character. Still the dialogue is wonderful, and the cutscenes do look good.
The RPG elements do work as well, getting different abilities and better weapons is fun, but they don't always feel like they're doing anything, so if you're looking for a challenge, turn the difficulty up a notch. There's very few bosses, and what there are aren't really a challenge. Even still, once again you'll be more than happy to be able to see that next cutscene, and not have to work through aggravating waves of enemies for it. The battles still look great and feel great.
One of the man downers this game has been said to have was the vehicle combat and driving. Personally I like how it handles, although it is a major pain when you have to drive it in a combat situation. The weapon is realistic in that it's firing arc can only shoot at such a range, but this does make battles incredibly difficult. Luckily you can usually avoid battles in this machine. When you get a chance to drive around tough terrain, depending on what your preferences are, it really can be fun.
All in all this is a wonderful game, made to last. I think the universe they created is believable, the xenophobia, the politics, the betrayal, the decisions, it's all here in one neat little package. This is a game you'll want to own, and play time and time again.