As we've said a million times before, Photoshop is the undisputed champion amongst image editors. The sheer diversity of uses and plethora of tools (including prepress industry standard tools) just make it a fact.
There are, however, a huge pack of second tier programs that include open source, freeware, and "the cloud" as it's been coined. These are often more than sufficient for the needs of the casual user, and with legitimate copies of Photoshop costing up to 600 dollars, the price of FREE can't be beat!
Even Adobe realizes this, as one of the first items on the list is the (marketing genius) referentially named "PHOTOSHOP.COM."
A few weeks back, I was working on a friend's computer and needed to do a fast edit on a photo before uploading. Alas, with no PHOTOSHOP on the computer I was sunk. Then I went to one of the image-editing sites and was able to make short work of it. I'm sure you'll find one that meets many of your needs nicely!