PhotoShop is the best. Period, end of story.
+1
Of course I have over a decade of experience with it and use it professionally so I may get a little better results out of it then the average user.
If all you want to do is simple resizing, minor color correction, brightness/contrast adjustments and such, then GIMP is your best value (and I would recommend it over Photoshop Elements).
But if you want to put in the time to learn it ... Photoshop just cannot be beat.