Godot is what I use. Godot is free, open source, small, and fast, and it's great for quickly and easily prototyping and building a game because of its solid features and scene tree component structure. It's also very fast and easy to export builds for different platforms. More games are being made in Godot every year. That said, it does have some weaknesses. It's not as good at photo-realistic 3d rendering, so if you want to make an "unreal" looking 3d game, you'll want to go with Unreal Engine. Another complaint that I've heard is that, due to how it's designed to use the clean, fast scene tree component structure rather than lots of imported global classes, it can take some getting used to, especially when working with multiple programmers on one project. Another argument that people have used is that the Unity dev community is huge, while the Godot community is small and it's hard to find help, but that's simply not the case anymore. Between the documentation, YouTube, Reddit, and Discord, I've had no problem finding help. If you're freelancing, then Godot is a no-brainer. You'll get a lot more done is less time, and you'll never have to worry about being forced to pay royalties or fees.