There really is no way to tell how Bush's first term would have turned out without the War on Terror. We might still be in Afghanistan (such an operation was already in the planning stages), but public opinion would not have allowed an intervention into Iraq (without 9/11 and the desire to destory Al Qaeda), which was what really made him vulnerable.
As a result, I would assume that Bush would make a slightly better performance then he did historically, but with the economic worries (if any still) came on equal ground, this is the result I would expect.
George Walker Bush : 321John Forbes Kerry : 217Basically, a comfortable victory in regards to the electoral vote, but there is a relatively narrow victory in the popular vote, comparable to the 1916 Presidential Election.