Naruto seems like a mix between Shik, and Lee. As he gets older the Kyubis Chakra merges more and more with his own making him stronger.

I'd put Naruto at 4th he certainly trains and without a doubt he is driven, but he doesn't put forth the same effort as others. With age he is inheriting the powers of the kyubi (Oro explained this...along with a few others) He does a quarter of the training of neji and an eighth the training of lee and yet gets twice the results.

What separates Naruto from the others is his drive. Naruto will get beaten to a pulp, be repeatedly knocked down, and still get back up. (yes, in part to the healing he gets from the kyubi) The only one who is more driven then Naruto is Lee.

Training
1. Lee
2. Neji
3. Sasuke
4. Naruto
5. TenTen
6. Kiba

Drive/Purpose
1. Lee
2. Naruto
3. Sasuke
4. Neji
5. Gaara
6. Dosu r.i.p 

Natural Abilities
1. Naruto
2. Gaara
3. Sasuke
4. Neji
5. Hinata
6. Shino