Adobe Photoshop is what most would say is the best graphics editor there is. However, it is pricey at $120 a year. Thankfully there are alternatives to Photoshop which can range from being free to $10 at most.
GIMP is an open-source image editor available for all platforms (Linux, OS X, Windows). It is free and the developers allow its users to change its source code to customize the experience. GIMP isn’t seen as a replacement for Photoshop. It is meant for hobbyists or amateurs. It also requires less hardware requirements than Photoshop. Everything is included: painting tools, color correction, cloning, selection, and enhancement.
The team that oversees development has worked hard to ensure compatibility too, so there are no compatibility issues. There’s also a very capable file manager built in that is like Adobe’s Bridge. The user interface has more of a learning curve compared to Photoshop as well.
Paint.net is image and photo editing software for PCs that runs on Windows only. It has most of the features that Photoshop has and doesn’t cost a dime. The focus is on ease of use, and there’s a definite tendency towards photo editing rather than artistic creation. There is a range of special effects available, allowing one to easily create fake perspective, blend and push pixels around the canvas, tile and repeat selections, and so on.
A good range of selection tools, support for layers, and adjustments such as curves and brightness/contrast mean that Paint.net is a great alternative to Photoshop for photo editing, especially if creators can get by without more recent additions to Photoshop’s tools.
This Mac-only program only costs $99 and is a professional vector graphics app for creatives and web designers specifically. With a simple UI, Sketch has many features like that of Photoshop CC, including layers, gradients, color picker, and style presets.
Its popularity means there are also plenty of community-created Sketch plugins that can be used to extend its functionality.
Photoshop Elements is a one-time paid version of Photoshop ($99) that is stripped down of some features and is seen by creatives as Photoshop lite. It targets mostly photography enthusiasts and not so much the creative as it doesn’t require a high-end computer to run. However, it has an Expert mode which is the closest to Photoshop CC’s normal working mode which includes features such as layers, masking and the host of common Photoshop tools.