User blog comment:Koveras Alvane/The Beauty of Mass Effect 2 Ending/@comment-5607736-20130429182345/@comment-256004-20130501100226

Randomizing plot is not a very good idea IMO, especially the ending. Random numbers are a great thing for gameplay and battles, but they are annoying when they mess up with the plot. For instance, in Dragon Age: Origins and Awakening, some companion sidequests relied on random encounters on the world map, and so if the random encounter just didn't spawn, you could never complete the sidequest. It was a pretty cool idea but it led to a well-known problem that some people just could never finish Velanna's quest line in Awakening because it was concluded in a random map encounter with a very, very low probability of occurring. Such things contribute nothing to the story but annoy the hell out of completionist players.

As for replayability, there are two types of it: one where you replays the game because you haven't seen all of its content yet and one where you have seen it all but liked it so much that you just come back to replay it again and again. Take ME2, for example. As my analysis above shows, there is absolutely nothing random about the Suicide Mission, so if you wish, you can have exactly the same playthroughs every time you start it. And indeed, that's what I, at least, have done: I have played ME2 from start to end three times (the most I've replayed any RPG, actually), making pretty much the same choices on each go--simply because I loved the experience itself so much.