Recommended Resources
Some cool stuff that you should check out if you want to develop amazing games!
Game Engines
GB Studio : An open-source quick and easy to use retro game creator for actual Gameboy consoles!
GDevelop : Create both 2D and 3D games for Steam, the web, iOS, Android, Windows, Mac, and Linux
Godot : Develop both 2D and 3D games with customizable plugins, cross-language scripting, and 32 / 64 bit compatibility.
Unreal Engine : Built by developers, for developers, with ideas that deserve to use the most open tool to bring it to life.
Graphics and Pixel Art
Krita : a free professional open source (better than Gimp and Photoshop) painting program for Windows, Mac, and Linux
Piskel : Online pixel art editor (this link allows you to use Piskel offline)
Tiled : 2D level editor that helps you develop the content of your game
Libresprite or Aseprite : a free and open source version of Aseprite for animating your game sprites
Sound Design
SForzando : A free soundfont player for your music production!
Reaper (not free) : A cross-compatible audio workstation for creating video game soundtracks (and anything audio related)!
hUGETracker : A very easy Gameboy music maker used for GB Studio!
Hammered : A fun handy Gameboy sound effects ROM used for GB Studio! Link goes to the tutorial