What are some alternatives?
When comparing GeeXLab and GDevelop, you can also consider the following products
Unity - The multiplatform game creation tools for everyone.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
LOVE - Hi there! LÖVE is an *awesome* framework you can use to make 2D games in Lua.
SDL - Simple DirectMedia Layer is a cross-platform multimedia library designed to provide low level...
Stencyl - Make iOS (iPhone/iPad), Android, Flash, Windows & Mac games without code using Stencyl.
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.