Though they can mean the same thing at times, they are also quite different in other situations.
They both can mean to value someone or something highly.
However, 'cherish' can also mean something more intense, something you think of with fondness or love. You can also cherish a memory - keep thinking of something positive.
'Appreciated' can mean the same thing, but it can also be neutral or even negative. It can mean to fully understand something.
"He appreciated the fact that he could be fired at any time." - He was fully aware of the fact that he could be fired. You would never use 'cherish' here.
Also, appreciate can mean grateful.
"He appreciated the gift." - You could use 'cherish' here, but only if the gift was very special and there was strong emotion associated with it.