You know... I've been thinking about this. What complex story? After I hunt down the clown who shot me in the head, what incentive do I have to side with anyone?
I enjoy the game enormously, but realistically... I found GTAIV and RDR to have a more complex (albeit more linear) storyline.
I think you are correct. The much-lauded story in F:NV is not complex at all. It's very straightforward -- Act 1 is following the clown in a linear loop; Act 2 is completing a series of missions for your chosen faction. (I have not (and won't) side with Caesar, but the quests for the others follow the same general pattern). Act 3 is the dam and dealing with the end boss. A player would have to be dense to get lost in that plot line.
I think that's a strength of the game. Because if one is a casual gamer without much free time they can play the main quest through, have fun, and get on with their life. But if one is a video game compulsive like me there are many rewards for straying off the simple path.
The thing that distinguishes FNV is not complexity. It's
details. Here the game shines, if you are the type of player who enjoys this sort of thing. That linear loop has a lot of sidesteps and can even be bypassed entirely. Those faction quests in Act 2 open a plethora of additional quests and fun characters. It goes on and on. I am on my fifth character and I'm still running across new stories and people I've never met. Details.
Another distinguishing factor of FNV is that it strives for believability by grounding the story in a mundane conflict. Squint your eyes, and this plot could have been set almost anywhere. The vast majority of protagonists are human beings and their motives are not dissimilar to ours. There is moral ambiguity -- each of the combatants possesses positive and negative traits. All the player's choices have negative and positive effects. This is very good stuff.
Oh yeah, you mentioned incentive. Yeah, that's a mild negative -- the factions promise rewards but they aren't too compelling. I imagine the designers expect that by that point the player will have met representatives of each faction and formed opinions. Or, maybe just the promise of more neat stuff to do is motivation in itself.
All unfocused rambling aside, what I'm saying is that the game is designed for casual
and obsessive players. It's designed for role players
and FPS fans (honestly, look at all the work they put into the shooting mechanics -- this game is a love letter to weaponry). Claiming it's one or the other and -God help us- smirking in superiority because you are a fan of one or the other is missing the whole point of the developer's efforts to make the game for everyone.