I have several photo editors. Each came with some piece of hardware I have either purchased or someone gave to me. 3- Scanners, 4- Cameras, 2- Printers, etc. not to mention the various freebie programs that came with 5- Computers. I have also purchased a 3 or 4 of them outright.
These include a couple of versions of Adobe PhotoShop, some free (crippled) versions and one commercial off the shelf one. I also have Photo Pro, PhotoOps, PhotoEdit, PictureIt, Cosmi Photo Plus, Serif PhotoPlus, LexMark PhotoImpressions, and a few other even less memorable ones.
NONE of them do "everything" and those that do kind of do most everything, do them rather poorly.
If you have a steady hand and a really good mouse you can use the paint tools (pencil, brush, etc.) in some of the programs to draw nice shapes over a photo to enhance the image or make simple changes, but I do not have the steady hand and usually ruin the image by a slight slip of my hand and put pixels where I don't want them.
Thus, for ME, the BEST editor for images is probably the most tedious to use and has the least number of tools and no general retouch functions at all. I use this one program to do the majority of the image editing that I do, and then use one or two of the others to try to blend out where I have inserted one image over another or painted something in (or out).
The following image is of my Aster 1:32 scale Mikado locomotive, nice soft white clouds in the sky and a green meadow behind it... and ME sitting in the cab!
I used three photos to do it. One was of the loco, one was of a distant image of the sky and a meadow, and the last was of me leaning on the railing of my patio deck pretending to be looking down the side of a boiler... the neighbor's must'a thought I was nuts as I put the video camera on a tripod aimed at the deck railing, pressed "Record" and then I stood on the deck and pulled an imaginary whistle cord, etc.... when I was done, I took one frame from the video to use for me in the cab.
What program do I use the most???
"MS PAINT", the venerable freebie paint program that has come with Windows since Windows 3.0 (or was it in 2.0?)
I wrote an article for Steam in the Garden magazine a couple of years ago to explain how I did it. (Issue 81 May/June 2005) There are a couple of neat tricks that make it fairly easy (if tedious) to do.
I find that GIMP http://www.gimp.org/ is a very useful image editing tool. I've used it a number of times to do just such an operation. It's also my primary tool for photo retouching, general cleanup, color tweaking, resizing, etc. Very powerful, and completely free.
For serious photo editing or special effects you're going to need a powerful photo editor such as Adobe Photoshop. Photoshop is expensive, but you can get started with Photoshop Elements for $80 or so. Then get a good book such as those by Scott Kelby. GIMP is a free alternative, but it has a very steep learned curve.
That said, I use Adobe Photoshop Lightroom for the vast majority of my photo editing. It can't do serious retouching, but for common tasks (organizing, cropping, rotating, color corrections, exposure adjustments, B&W conversions, etc) it's so much faster and easier than editing one photo at a time with Photoshop. There's also Apple's Aperature which is similar to Lightroom.