The thing is while I get the Obama = Carter meme is popular since that was the last Democratic President who was an abject failure, there really aren't much points of comparison at all. The characteristics of the Carter administration (in popular perception) were rising unemployment, a disastrous foreign policy, out of control inflation and a complete lack of legislative accomplishment. How do any of those match up with the current incumbent?
There are plenty of Carter parallels. High unemployment. High gas prices. An "America follows" anti-exceptionalist foreign policy. A gridlocked Congress leading to few legislative accomplishments in his last few years.
Carter had his policy successes, too, including the Camp David accords and creation of the Department of Energy. To say that there was a complete lack of Carter legislative accomplishment isn't true. The economy and foreign policy sunk Carter. Republicans hope Obama will meet the same fate for much the same reasons.