George Bush won a landslide in 1988 and got 53.4% of the vote. In 1984 Reagan won 58 to 40% and it was the biggest landslide in history. I would consider anything over 53% for GW a Kerry ass-whoopin'.
I'd agree with the Electoral College rout being a landslide. I'm just not comfortable with the numbers; anything below 60% and the left will continue screaming that "Bush Has No Mandate!"