If you’re in the camp that looks at retro games and wishes that they had a true widescreen option that doesn’t rely on weird stretching techniques, then emulators like WideNES and now Wide GB might satisfy that need.
Based on a modified version of sameboy, Wide GB includes an extra option: “Use Widescreen”. Enabling this option extends the screen boundaries of the game: you can then resize the window, and use the aspect ratio you wish per its developer.
As awesome as this sounds, there are caveats when adding this type of unintended functionality to a retro game. Since widescreen was never intended, the emulator basically learns as you play, saves areas already visited, uses heuristics, and stitches everything together to create a fake widescreen image. (Great simplified explanation) It also attempts to apply translucency to the HUD.
This means that upon the first boot, you may not see anything out of the ordinary, but as you progress, the coding should start doing its magic. Like Frankensteins monster, it will likely not be seamless even if it’s a miracle of sorts.
For now, an OSX version is readily available with a Windows version “coming soon” for players to try.