Unreal Engine 4.1 Update Preview

I think it really started with the Humble Indie Bundle's mandatory Linux support, accelerated with the help of Unity and Kickstarter, and really achieved mainstream legitimacy with Steam. As long as the GPU manufacturers cooperate and write good drivers, the future looks very bright indeed.

Also...you forgot Source.

Plus, unlike Unity, you could theoretically port it yourself. Paying $20/month gives you complete access to the source on GitHub, and they're going to start accepting pull requests very soon.

If you want to make 3d games for major platforms and are of moderate to high programming talent, it's hard to beat Unity at this time. The Unity Asset Store is an inexpensive source of great starter projects, temp assets, and commonly needed libraries.

That said, making 3d games at all is deeply nontrivial and I wouldn't recommend it as a solo hobby owing to the very large surface area (art, design, game design, geometry, game logic, tooling, etc.). You can get to the 85% level in everything but modern consumers will be unsatisfied with the quality.

For 2D, especially for getting to a shippable product, I might try LOVE or Moai, although both of those are on shakier foundations support-wise. Don't let anyone tell you having anything to do with Python.