this is going to turn into a "mine is bigger than yours" debate, probably...but i'd say: if you can afford it, get photoshop. if not, whatever suits your price range. also depends on whether you just want to do graphics etc for on-screen (web, cdrom, etc) or for print (in which case photoshop is the best solution)...
if you're an absolute beginner with no budget, you could always give the gimp a whirl
http://www.gimp.org/