I'm not sure I even understand this site, but based on what I see, how can one tell if a cipher is a good one-at what level is it considered good?
By cipher you could mean many things. What comes to mind is substitution (every a is __, every b is __...) but I don't think that's what you mean. I think you mean encryption algorithm (eg: AES, RSA, etc.) the unit of measure for security there is entropy.
And if you mean substitution, that is not at all secure and should almost never be used unless it is a PART of another algorithm.