MD5, SHA, CRC, are all one-way hashing algorithms. They only contain a fingerprint of the original data. The whole point is that if anyone gets a hold of the hash, it can never be reverted to plain text. With hashed passwords, the user enters a password, you hash it and compare the hash with the one you have stored. If they match the password was good. You should not try to give the users their password back, but you CAN let the user change his password if he has forgotten it. Verify some other info and let him change the password. This way if someone else changes it, the real user contacts you because he can't log on anymore.
Plain text passwords have been mostly extinct for the last 20 years.