G.W. still had an approval rating above 50% then, you have to remember that; It was before Hurricane Katrina which made it plummet (It's under 30% these days, according to a couple Of sources I've read). The difference between him and McCain is that McCain has many similar policies than Bush, and Independents will thus probably vote for Obama.
Also, I think that the Electoral College isn't a good Idea, seeing as the majority of people can want a candidate, but the other win. (i.e., the 2000 elections)