You’re right that I don’t like to go down this path, and the main reason is that it’s far too soon to give a solid judgment on President Obama’s entire term. It requires several years to pass in order to give an adequate ranking of a Presidency and a President’s enduring legacy.
With those caveats out in front, I’ll say that if Obama loses in November and becomes the first one-term President in 20 years, he’ll probably be ranked for some time as a slightly below average President — in the Taft/Hayes range.