I would have to agree, i think that they COULD possibly be pretty close to the 1st and 2nd hokages power/skill but the 1st kage was strong enough to fight madara,control the bijuu's and had a bloodline limit (to control wood i think) and the 2nd kage was really good with water.
Together they were really good for element combo attacks.
If Naruto and Sasuke learned a few more jutsus, and trained a little more, i would say that they would be stronger then anyone at kage lvl, they would be on their own lvl that surpasses that of the kages.
Naruto of course would still be the stronger of the two.
NOTE: the 3rd hokage was able to fight the 1st AND 2nd hokage PLUS Orochimaru, and he was like 80 yrs old and he beat the 1st and 2nd kage