As of now I see edo madara as 1. Tobi as 2. Naruto as 3. Sasuke as 4. Right now there is a big power difference between 3 and 4 for now but I imagine by the end naruto and sasuke tied for 1.
sasuke will probably gain the rennigan and become the strongest but then naruto will combine sage mode with perfect kb and get new jutsus and become completely unstopable