Between Sasuke and Nagato, Sasuke wins. His sussano is quite powerful, he may not be as experienced as Madara with Sussano, but he clearly is extremely good with it and it is likely its a PS. PS is on the level of the more powerful bijuu. A normal Sussano as a defense blocks most things Nagato can dish out and I don't think Nagato is physically strong enough to break it. I dont think Nagato has any move to get past a PS though.
ANYWAYS, even though Sasuke beats Nagato, why would either be in the top 5?
The top five ninja we have seen are clearly:
1. Itachi
2. Obito
3. Kakashi
4. Hashirama
5. Madara
And Sasuke and Nagato aren't even on the sixth or seventh spot because at the very least Naruto and and Minato take those spots. At the very least they are fighting for 8th place.