I have been in the game industry since 2000 and while most 2d art positions I have seen require knowledge of Illustrator, in these 12 years I have had to use it exactly once.
This is not to say that the ability to create vectorial assets is not important. But it happens that I have usually relied on Flash or Photoshop to do it. It’s more simple and easier to integrate in the final product (the game.) I realize that knowledge of the vector tools in Photoshop is not that widespread and that’s why I filmed this small tutorial to get you started. There are many other possibilities, and they are yours to discover.
I hope this helps. Unfortunately, my Photoshop is in French, so maybe I’m not using the exact same names as in English.