The reason I think 3d will stay a fad for the time being is because of the glasses and the cost. I still know plenty of people who watch tv in sd and those who got an hd set only got it recently. I don't see these people replacing their recently acquired hdtv for a 3d set any time soon. And the glasses? Really? In the decades of progress since the sub-medium was introduced, we still have to use the glasses. I understand why, I just find it hard to believe that all those clever minds never found a way around it.
This is pretty much my thought on the matter. Those glasses are especially annoying when you already have glasses.
To me, though, 3D's boon is in the small details. When I went to see the Avatar preview event last August I got to see it in IMAX on 3D. The only part that stood out was when the lead character was being chased through the jungle by the lizard-tiger-thing. I've seen such scenes in plenty of films before, but the difference here was the 3-D made all those bits of timber and dust stand out. All of a sudden things seemed more explosive, the sound matched even more closely with the visuals, and it gave the impression of damage down.
Now let's apply that level of detail to a video game with bullets whizzing past your head, explosions drawing up dirt or bits of water and blood splatter. Granted I'm using it in your generic FPS as an example, but the immersion factor is increased drastically.
However, those glasses are uncomfortable enough that I could do without, thank you very much. I'd rather 3D not be part of my gaming until 1) I get contacts or 2) we don't need the glasses. If I haven't done 1 by the age of 25, then there's no chance I will ever.
While its nice, I think that 3D may not catch on because it isnt an end product of a long series of develpoments. HD is the current product of getting Better Visual, Sound goes the same way.
Also, 3D makes my head hurt, so perhaps I am biased.