Here's my strongest characters list. It does not include the Sage of Six Paths because he has never been on any fight up until now. This is all based in my thoughts so please respect that. You can post your own list but i would like you to put some arguments. And don't hate please.

#1- Hiruzen Sarutobi
Said to be the strongest hokage that konoha has ever produced and the strongest kage of his time during his prime, and was able to fight two hokages at the same time plus Orochimaru and still defeat two of his opponents, even at his old age.

#2- Hashirama Senju
Able to defeat Madara Uchiha, so he's a top tier shinobi. He could also control tailed beasts as if they were pets.

#3- Third Raikage
Greatest raikage ever seen, and fought toe-to-toe with Hachibi. Managed to hold and entire army consisting of 10.000 ninjas for 3 days and 3 nights before collapsing.

#4- Madara Uchiha
Strongest Uchiha ever produced, and was almost an equal to Hashirama. Could control Kurama.

#5- Nagato
Able to destroy a village with just one jutsu. Would be able to defeat Killer B and Naruto if Itachi didn't intervene. If the secret of his jutsu was not discovered he would be able to defeat Naruto during the invasion of Konoha.

#6- Minato Namikaze
Was able to become hokage despite his young age and was able to defeat Tobi. If he didn't sacrifice himself for his son, he would have managed to mix his element with the rasengan by now.

In between #6 and #7 is Tobi. Tobi is pretty strong, but when his opponents discover the secret to his jutsu is discovered, he rates bellow #9.

#7- Killer Bee/Naruto/4th Raikage/Onoki
I can't really give and explanation on this since it's about 3 very different characters, but the way i see it, these 3 are about equal on power, but Naruto has the greatest potential for improvement since only now he managed to control his tailed beast.

#8- Jiraya/Itachi Uchiha/Mei Terumi/Hanzo/Kisame
Jiraya was one of the few that could enter sage mode and Itachi was basicaly the perfect shinobi. Even tough Itachi claims that Jiraya is more powerful than him, i think they are on equal footing.

#9- Kabuto/Orochimaru/Kakashi/Might Guy
These guys are just plain badass, no more arguments needed.

#10- Sasuke Uchiha
Sasuke is strong, but he can't win against any of the characters above because of his cockiness. The only fair fight I've seen in Part II so far was his fight against Deidara. After he got Mangekyou he would have died atleast 5 times were it not for the help of Juugo, Karin, Zetsu and Tobi. When Danzo used Reverse Four Symbols Sealing Technique he would have died if Tobi didn't warn him to get out.