Should Comey resign? In my opinion, and in a word, No. At least not at this time. I offer two (2) reasons.
Firstly, as a practical matter, "better the devil one knows..." especially when his successor will be chosen by a man who may, himself, be the target of an F.B.I. investigation.
Secondly I can envision a scenario where Comey made a mistake in judgement, very much like Hillary, without criminal intent. He spoke publicly about finding a new source of emails, admittedly a big, big mistake but which, in his mind, was a minor matter since he had already declared her as not having committed any prosecutable offense. On the other hand, he may have been aware of a really big matter shaping up with possible "high crimes and treason" on the part of the Republican candidate and members of his staff, which would have made the email matter really inconsequential.
We know Comey was wrong in his judgement but we have no choice but to wait to see what the F.B.I. does about Trump before we start clamoring for Comey's resignation.