All are great. Except :
Inkscape is decent, except that it's nowhere near illustrator. It's got issues. Issues that maybe casual users can tolerate. A more demanding user won't.
Gimp really isnt a substitute for photoshop. It's slow, unstable and ux is dogshit. Too bad.
It's a lot more fully featured. It's allows for a lot more complex mixing and editing. It supports a lot more plugins including virtual instruments. Audacity is good for basic recording and mixing but Ardour takes it to the next level in terms of versatility and control.
I agree these are alternatives, although for the larger solutions, I would argue that none of them are comparable for professional users, besides maybe Blender. I know many animators that use it, but it's more like a tool for a specific purpose, while they also simultaneously use many other proprietary programs.