What were the first 2 video games ever to be registered in the Copyright office

This would be a difficult question to answer unless you happen to know who were the authors of those games.

Registration in the US copyright office is not required until you want to sue someone, and that has been the law since at least 1909. Works published with copyright notice prior to 1963 did, however, require renewal filings after 28 years, so you might find a renewal filing for copyright of an early video game.