What are the best OpenGL alternatives?

Vulkan is a new generation graphics and compute API that provides high-efficiency, cross-platform access to modern GPUs used in a wide variety of devices from PCs and consoles to mobile phones and embedded platforms.

WebGL is a cross-platform, royalty-free web standard for a low-level 3D graphics API based on OpenGL ES 2.0, exposed through the HTML5 Canvas element as Document Object Model interfaces. Developers familiar with OpenGL ES 2.

A refreshingly simple data-driven game engine built in Rust. Free and Open Source Forever!

Microsoft DirectX is a collection of application programming interfaces (APIs) for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms.

Allegro 4 and Allegro 5 are cross-platform, libraries mainly aimed at video game and multimedia programming. They handle common, low-level tasks such as creating windows, accepting user input, loading data, drawing images, playing sounds, etc.

GDI++.dll is a replacement for the Windows default font rasterizer, which gives you a better font-smoothing capability, just like Mac OS X.

Amethyst uses gfx-rs to render graphics with Vulkan or Metal. It is meant to be used for 2D and 3D, with various utilities for both types of games. It should be beginner friendly but also allow more advanced uses such as custom render passes and GLSL shaders.

Metal provides near-direct access to the graphics processing unit (GPU), enabling you to maximize the graphics and compute potential of your apps on iOS, macOS, and tvOS.

Mantle is a graphics API specification; the software component that makes it easy to apply programming techniques and optimizations written for consoles to PCs with Graphics Core Next (GCN) Architecture.

Crystal Space is a mature, full-featured Software Development Kit (SDK) providing real-time 3D graphics for applications such as games and virtual reality. It is free (LGPL) and cross-platform (Windows, GNU/Linux, Mac OS X).