Let's first define who we call a complete actor. Anyone who 1. Can do any type of role (His/her range must be large enough to cover almost all types of roles) 2. has a decent and presentable personality 3. has high speach skills (pronounciation) In this set of parameters, personality should have lowest weight. if we put all actors through this list, we will find that most actors will not pass the test. For example: SRK has a limited range, he can do mushy roles better.Akshay kumar has bigger range then him. Amir's range is also limited. He has yet to convince in a role like 'Bazi'. So, SRK, Amir, Devgan,Dutt, Saif etc keep doing similar type of roles which they think they could do. This is not wrong, but this creates an impage among people, which takes over the acting skil issue. These actors will sell until that image sells. Becuase of this image, they become over rated. I think, SRK is the most over rated actor, then Saif, next is Aishwarya Rai.
Among those who would fit well in the parameter above are Dilip Kumar, Amitabh, Naseer, Paresh Rawal, Om Puri, Hritik Roshan (would be intersting to see him a comic role), Shabana, and Vidhya Balan.