For pixel art:,For vector illustrations:,For 3D:For Voxel:I personally don't use Illustrator as for me as a hobbyist it's too expensive. But this is something everyone has to decide on their own. I included it in the list because it's a top software and industry standard of course.In the end it's, at least from a hobbyist perspective, not so much about what tools you use as how well you know your tools and about your creativity.
Isometric Pixel Art Tutorial
Best Pixel Art App Android
All tools listed are powerful enough to create something great.