I don't know that. Most of the game data is occupied by sprites/images. I use WinRar for compressing the files. If 7Zip compresses it that much then I must give it a try.
Yep, 7Zip is pretty much the go-to application for achieving the highest amount of compression rate without going forward with more advanced compression methods, such as packing the game into an installer/setup. (And it's probably not worth it either)
