I don't believe that..and here is why.. anyone can become a good manager with learning, experience and practice. To be a leader you need to have some special characteristics which you can not learn, experience or practice.. for example, a company is going down, a good manager can do some marketing or financial magic and bring the company back into game.. but only a good leader keeps the employees and customers motivated, gives them strength and makes them keep faith in their management in adverse times..
Such as for a leader of a community, revolution, a nation.. a leader is one who has a vision, who has a belief, who has the strength not only to stay focussed but also to lift the spirits of followers up when everything is going against them.... but "as a diamond without being cut and polished won't shine so is a leader without knowledge and understanding"
The example i chose happen to be a leader who is also a manager but this need not be the case always...
A leader may not be at a higher level in the social, technical, managerial ladder...but always at the top leading the group, where he belongs to, lives or works
If you observe some of the leaders the world has seen so far, all great leader have some basic skills/attributes:
1. Knowledge: Clear understanding of the system, their goals/beliefs
2. Communication: All are great Orators
3. Judgement: Decision making skills
4. Selfless: they identify and nourish talent
5. Creativity: Imagination.Vision and creativity
6. Perseverance :motivated by a cause, to bring a change
I might have not use the right words, sentences but i've expressed myself... Anyone can be a good manager, only a few can be leaders