Yep CmDr_RavEn has an excellent point, we have gotten to see very little of either.

The main reasons I have for choosing the 4th is that you don't get to be Hokage for nothing, especially to replace the 3rd! If the 4th had reached a strength greater than the 3rd due to the 3rds advancing age (13 years earlier?), then the 3rd nearly defeated Orochimaru AND the 1st AND the 2nd .. after getting OLDER... then .. I would say that the 4th must have been one hell of a force to reckon with.

Itachi seems very over-rated. The reason? He has goals, he came for them and FAILED. He had to run away twice already. This is an indication of his intelligence, which I would rate as high, considering he doesn't want to risk defeat against very powerful opponents. This is also an indication of his weakness, because if he was truly god-like, he would simply have already taken what he wants.