Zhukov said:
The elements of choice serve more as seasoning on a predetermined story rather than "player driven narrative."
If I may expand on this: If you take a step back and push aside all the characterization of Shepard and all the NPC's, ultimately there's no choice in what happens. You get to make these big decisions, like, for example, destroying the Collector base in ME2 or handing it to Cerberus, but that doesn't make a huge difference as to where the story's going. Mass Effect was exceeding at one thing, tho: Making it look like you would really change the course of the story.
This illusion of control came crashing down with the ending of ME3 - this especially since in all endings, the mass relay network is destroyed, the Normandy and surviving crew end up on the same jungle world.
I think it was in one of the early interviews where Hudson went on about how they didn't need to make the endings as similar as the ones of ME1 & 2 since every other game would take place during or before the Shepard trilogy. If they had leapt on that opportunity and created the "wildly different conclusions" they were going on about, the impact of the... unexpected matter of the Catalyst starchild would have been lessened.
On the other hand, if Mass Effect had just been presented without the possibility of making your little choices along the way, I think the series as a whole would've lost a lot of its appeal.
You could try an experiment: Set up a new game in ME3 and play in "action" mode for a while - from what I recall, this mode makes all the conversational choices for you, and you're only required to kill stuff. I don't think it will be as much fun.