So, I finished Fallout: New Vegas around Christmas. Or at least, that is to say, I chose an ending arc to the game, and since it was the first one I played (achievements make me compulsive and I expect to spend another 20 hours in the game in 2011 unless there's DLC, in which case it'll be a lot more) it's the one I'll always feel is "real."
The rest is behind a jump, because there are significant spoilers for the plot and most characters.
There are four ways you can choose to end the game: supporting the Legion, supporting Mr. House, supporting the NCR, or overthrowing all parties (working with Yes Man) and supporting a theoretically benevolent anarchy. I knew from the start that the Legion was right out, and at a certain point near to the end of the game, went back to The Fort (as Render Unto Caesar Part I is actually an integral quest to most versions of the plot) with Boone and shot the hell out of everyone. Taking down Caesar felt good, and I liked that it actually got onto Mr. New Vegas's sadly me-deficient newsreel.
(Yes, I am an egomaniac with my Fallout radio. And?)
After thinking about it at great length, I decided Mr. House was a problem. And in order to advance in the game, he was a problem that had to be eliminated, rather than ignored, so I went and disconnected him. Felt pretty shitty about that, actually, but it had to be done.
But I spent several days after that trying to decide whether I wanted NCR rule, or a Free Vegas. I went around and did every quest, uncovered every location (except Quarry Junction -- even at level 30, in Power Armor, those damn Deathclaws take me out), and got everyone ready for the Battle of Hoover Dam. I felt like a total badass, having the Brotherhood of Steel, the Enclave, the NCR, and a bunch of others all lined up to fight on the same side.
But... whose side was it going to be?
Where the game challenged me was philosophically. I spent days trying to decide which I felt was better: an overly strict, martial government with whose rules I didn't necessarily agree, or a city-state left to develop its own system and status?
Ultimately, I chose for the NCR. I looked around at everything I could find in the Mojave Wasteland, and it came down to this: there were too many powerful players already on the field, and the citizenry needed some kind of unifying umbrella and protective force. The NCR isn't ideal, but I didn't trust that most people could survive the Fiends, Legion, and other raiders without being forced to work together.
In my head there's a lot of NCR reform over the next 5 - 10 years, though, as actual governance starts to become an issue in a rebuilt, unified West.