I don't have any of them, though I used to use CorelDraw a decade ago. So grain of salt, and you probably heard most of what I'm going to write, but, anyway...
What's best depends on what you're going to do. Are you going to hand draw the images, trace photos or jpgs, or make a collage of a bunch of pre-existing images?
Photoshop is primarily a bitmap photo editor, with Elements doing ~90% of what the full blown CS4 version does.
Illustrator & CorelDraw are primarily vector based editors.
So if you're starting with pictures, and want to edit or collage them, Photoshop is the better choice. It also is the most used of the three apps, so you'll find online help more easily than the others. If you go photoshop, you probably only need the elements version, depending what you want to do, of course. I've heard it's easier to learn than CS4, too.
Illustrator is the more popular of the two vector editors you asked about. Both are better for tracing and hand drawing, but I don't know them well enough to recommend one or the other.