2d art: probably photoshop or corel painter
3d art: from personal experience I would say maya and zbrush are my favorites but I havent tried all software.
animation:maya

model design: a paper and pencil

everything is 3dgs compatible (more or less through one pipeline or another) I have found that if you want to make something compatible with 3dgs its more of a "where there is a will there is a way" type of mindset. I have seen content come in from all sorts of software.

You should check this out if you havent seen it already:
starving game developers list from OrangeBrat