Well, if this is your first attempt at spriting, you deserve some leeway. Here are some beginner's tips:
-Don't use the default MS Paint colors.
-Don't use the Circle Tool to create circles. They just don't come out right; it's easier and more effective to create them manually.
-Use references. This goes for most types of visual art anyway, unless you're purposely trying to avoid using them.
-There's a lot of empty space on that sprite sheet. When assembling sheets, try to have as little empty space on them as possible, compacting the sprites into an overall smaller space.
-When saving your sprites, do not use the file type .jpg or .jpeg. This will make the sprites blurry. Save as .png or .bmp in most cases.
All that said, there are many problems with these sprites. The starman, mushrooms, the opening sprites of the pokeball, the heart container, some of the melee weapons, the koopa shells, and the barrel are all misshappen. The barrel doesn't really look like anything but a brown shape. (This is where using references comes in.) Also, there is absolutely no shading on the sheet.
Those are the most immediate things I notice, but these sprites definitely need to be worked on, or redone completely. You have a long way to go. That's okay, though. No artist gets good without practice.
-Don't use the default MS Paint colors.
-Don't use the Circle Tool to create circles. They just don't come out right; it's easier and more effective to create them manually.
-Use references. This goes for most types of visual art anyway, unless you're purposely trying to avoid using them.
-There's a lot of empty space on that sprite sheet. When assembling sheets, try to have as little empty space on them as possible, compacting the sprites into an overall smaller space.
-When saving your sprites, do not use the file type .jpg or .jpeg. This will make the sprites blurry. Save as .png or .bmp in most cases.
All that said, there are many problems with these sprites. The starman, mushrooms, the opening sprites of the pokeball, the heart container, some of the melee weapons, the koopa shells, and the barrel are all misshappen. The barrel doesn't really look like anything but a brown shape. (This is where using references comes in.) Also, there is absolutely no shading on the sheet.
Those are the most immediate things I notice, but these sprites definitely need to be worked on, or redone completely. You have a long way to go. That's okay, though. No artist gets good without practice.