I'm going to go against the grain and say that while Photoshop is likely the most complete set of software for image post-processing it may not always be the "best", as that qualification depends largely on your personal needs. I heartily recommend Lightroom (current version 5) for anyone who is just starting down the road to the digital darkroom. It's extremely simple to use, more intuitive than PS, and is starting to get the tools to make it a real competitor with PS for the amateur photographer. I would venture to say that I could live with Lightroom alone for 90% of my post processing. I've found easier and quicker ways to do things in other software (spot adjustments, noise reduction and sharpening), but if I had to I could do it in LR alone.
It's also a great organization and workflow management tool. I say start with that and then see where you might want to go that you can't and tack on the appropriate additional software then. Photoshop as a first stop can, and almost always will be very daunting.