It's funny that all of the people who support Obama have a tendency to ignore any facts that they may find hard to swallow. So here's a quick list of why Obama is four more years of Bush:

Bush: Supported government involvement in education.
Obama: Supports government involvement in education.

Bush: Supported Medicare and Medicaid.
Obama: Supports Medicare and Medicaid.

Bush: Supported more government spending and regulation.
Obama: Supports more government spending and regulation.

Bush: Supported the Wall Street Bailout.
Obama: Supports the Wall Street Bailout.

Bush: Supported the War on Terror.
Obama: Supports the War on Terror.

Bush: Broke all the promises he made when he was first elected president.
Obama: Broke all the promises he made when he was first elected senator.

Bush: In favor of nominating biased supreme court justices.
Obama: In favor of nominating biased supreme court justices.

That's all there is to it and a bumper sticker from cafepress.com sums him up well:
"Obama '08: Get disappointed by someone new."
Don't take my word for it, just head to the Cato Institute for an in-depth look at what I just said.