The best part about these option choices is that you have control over the story. Do you want to make the noble choice or do you want to make bad-ass choice. To each his own and Mass Effect delivers this.
Let's talk about the conception and design of this mechanic. Have you ever wanted to play a game and you wanted to just kill a character right there? Or have you ever played a game and a character died and you wanted to save him? That is the main motivation behind this game mechanic.
It's a really neat idea and Bioware implemented it. It's really easy to think of this feature in your basement and say how cool it would be. It's a completely different thing to actually do it.
For all of you game designers I will tell you how the mechanics work. Basically what happens is when you make a choice in the game it adds points to the Paragon or Renegade variable. So if you make a Paragon choice and you receive a +5 for that choice, it just simply adds 5 to the Paragon variable. The code probably looks something like this.
int paragonNumber = 0
if helpHannar == true
paragonNumber = paragonNumber + 5;
Of course that is a gross over simplification of the entire process but the basics of it are there. The cool part is unlocking menu choices. All that is happening here is that when the paragonNumber is above a certain value it will unlock a choice.