Basically, if the 2D version is crap, than a 3D version will just be crap in 3D.
The 3D version has some well realised effects that make it possible to sit through what is, at best, a rather average plot.
The ensemble is worth seeing in 3D, there's nothing illogical about that. If I wanted to watch something on my TV, I'd plump for so many others in its place, but on the big screen, it fares considerably better.