I really wanted to post a reply to this thread on another forum but I wasn't a member there.
Underrated: Sai, he was one of the main fighters in the root and yet he does not get a single fight devoted all to himself.
Overrated: Orochimaru, Itachi and Sasuke defeated him in a minute or two but yet Sarutobi and Jiraiya couldn't defeat him. Itachi said that Jiraiya is on a different level than himself and that Jiraiya couldn't defeat Orochimaru. He is weak and yet he is so strong. What is he?