JPG, 296KB, 800 x 690px
This image looks the second best in my opinion.
PNG, 1.14MB, 800 x 690px
This image is the best quality in my opinion.
GIF, 479KB, 800 x 690px
This image looks the worst to me. In the moss you can see slight pixelation
JPG, 66KB, 511 x 365px
PNG, 55KB, 511 x 365px
GIF, 49KB, 511 x 365px
My eyes can't see a noticable difference in quality
When converting a gif to JPG/PNG you get a series of still images that make up the animation frames.
The PNG (first) is darker because the transparency allows the black background to show up. The JPG's (second) brightness increased the greater the transparancy was set to, and the GIF (third) only became slightly brighter.
Each format has it's benefits depending on what you need to do. Below is some more info on each filetype
This is a lossy file type. Because of this, it loses quality when it undergoes editing, and compression/decompression. As a result, a meme sprouted making fun of people who share low quality JPEG photos. I would use this filetype for images where detail isn't as important such as the basic graphics
More Info Here
PNG is useful when need to maintain quality of images. PNG is a lossless filetype. It is also useful when you need transparancy of an image. I would use this for the highly detailed image.
More Info Here
Better suited for graphics with little detail, and for animation of images
More Info Here
Relax with this wonderful desktop image