As a graduate of his University, I am duty bound to disagree with you about that. Wikipedia, an unimpeachable source if ever there was one, has him in the top 5 or so presidents. Historical rankings of Presidents of the United States - Wikipedia, the free encyclopedia

I really have no idea how effective he was as President. The last time I took a history course was in high school in 1974 or so. All I know is that Mr. Jefferson is, and always will be, The Man in Charlottesville.