So Pixar's releasing 3Dified versions of Toy Story and Toy Story 2; James Cameron is planning a 3Ded Titanic, and possibly Terminator 2 for good measure. In recent years we've seen 3D sequences in 2D films like Superman Returns and Harry Potter and the Order of the Phoenix. In our 20th birthday issue, Guillermo del Toro, JJ Abrams, David Fincher and Paul Greengrass all expressed enthusiasm for the 3rd dimension, which Robert Zemeckis and Spielberg are already embracing. 3D is here to stay - and the technology behind it is only getting better, slowly laying to rest all those complaints about eyestrain and so on. So the question becomes not whether 3D films are going to be with us for some time to come, but which films should be 3D, and whether any older films should get the third-dimension treatment.

While the Toy Story films and their Pixar brethren were originally animated in a quasi-3D environment, so that they require only the addition of a virtual second camera for stereo-vision, most films don't have it quite that easy when it comes to inflating the images and giving them that extra oomph. And it's not just a question of picture but of the whole shooting technique. In 3D to date, there's a clear difference between the films that were designed with 3D in mind, and those that merely transfered over. Consider the difference between an Up or a Coraline (neither of which particularly relies on 3D trickery, but both of which are enhanced by it) and a Superman Returns or Potter, both of which had action sequences in 3D that are clearly not shot with the format's strengths and weaknesses in mind. The opening air crash in Superman Returns, in particular, demonstrates (to me at least) that shaky cam and 3D are and should always remain incompatible. I'd rather watch Journey to the Centre of the Earth 3D and its 3D-sploitation over and over than sit through that again.

2D animation going three-dimensional faces similar problems. Judging by the several minutes I saw of Beauty and the Beast 3D at Comic-Con this year, it's going to take some getting used to. The problem is the difference between the smoothly-coloured cell characters and the more textured, detailed backgrounds that jars somewhat when the characters are given extra depth and weight. After a few minutes I could feel myself settling into it, but it's got a harder road to acceptance than its 3D cousins.

And what about 3Ding* live-action? Are there films that would genuinely benefit from it? Titanic and Terminator 2 won't suffer, probably, especially with 3D messiah Cameron at the helm, but no-one's suggesting that, say, The Bourne Supremacy get the same treatment. Similarly, George Lucas mooted a 3D Star Wars years back, and some fans are still drooling from that day to this.

It's worth noting here that there have been mutterings from Hollywood recently that 3D is not just for action movies**, although that remains the focus of most of the attention. So what existing films would you like to see it 3D - or is it up there with colourising black-and-white films for you? Should we be looking at Citizen Kane (well, it's got some great camera-moves and it was certainly innovative for its time)? Should we, like Cameron, draw the line in the early 1990s? Or should we leave well alone and save the silly glasses for the new kids on the block?

*I'm still looking for the right word for this.

**Alfonso Cuaron reportedly wants to make a completely actionless movie in 3D, so impressed was he with the footage he saw from Avatar and so convinced that it's not just for blowing shit up.