A valid point, and one which I made in one of these threads a few weeks ago regarding videogames that can be played in convincing 3D using eDimensional and other systems.
But there is, I believe, more 3D information in videogames (displayed in 2D) that permits changes of vantage point and perspective in game.
In the case of animation where live actors are employed, the effects of 3D conversion may be more complex. In the case of such live/animation films unless the 3D conversion is considered while shooting, the problem is that the director makes choices concerning what to focus on...where to "lead the eye." When you convert to 3D some of this is lost or altered in ways that may be jarring.
It's also sometimes the case that in these 3D conversions, you have an effect of characters and objects appearing in separate planes, like those popup books that are "3D" in a sense, but lacking some important depth and parallax cues.
Going back to videogames, it is the player who constantly chooses the character's vantage point (and what to focus on), and the programmer puts enough information into the game to allow for realistic changes of perspective. In a film, the director makes these choices in a way that is somewhat unalterable.
Anyway, interesting stuff, and DLP is apparently the best technology for viewing 3D at home. But there have been some recent advances in holography that will probably make (as usual) science fiction a pretty reliable form of literary prophecy.