kakashi is not the strongest shinobi ever...the first time we see orochimaru's true face in the anime, kakashi was shaking in his sandals. I can say dis right now Jiraiya is stronger than him n no one in their right mind would disagree with that statement. In the argument on who the strongest shinobi of all time are the names that should be a part of it are:
1. Madara
2. Pain
3. 3rd hokage(younger)
4. 4th hokage
5. Itatchi
6. Jiraiya
7. 1st hokage
8. 2nd hokage
In time i think naruto n sasuke will surpass all of these great shinobi. kakashi is definetly strong n he has alot more time to get stronger because hes only 29....if he dose'nt get killed by pain first. His chakra capacity is not good at all, hes lucky that he has 1 sharingan n not 2 cause his body wont be able to handle it. sasuke even perfected kakashi's only original jutsu, with the full body chidori. At this point i can say that sauke is even stronger than kakashi.
In time sasuke n naruto will surpass all of these great shinobi
