Some people believe that Obama is the worst president ever. Maybe, maybe not, but let's acknowledge something.
"Best" and "worst" are merely terms that get applied to inspire debate without the possibility of empirical resolution, but suffice it to say that over the course of over two centuries every single one of the 44 occupants of the Oval Office* has been viewed by some portion of the American citizenry as the worst president ever—and likely that started while he was still presiding over the Executive branch. The same "worst" moniker was used for George W. Bush during his time, and was attributed to Clinton in his time… and you get the idea.
So while there can never be absolute agreement about whether our current Commander-in-Chief or one of the previous 43 is the "worst" person to hold that title, it's difficult to argue that the leading candidate for that "worst president ever" role will someday be replaced by a president in the future.
Whether Obama's tenure lasts two more years or six, eventually there'll be a new person behind that desk who (in the view of at least some) will be screwing up the country in ways that we, in 2010, cannot yet imagine.
The future's so bright I gotta wear shades.
* Using this figuratively. Obviously some preceded there being an Oval Office.