Napoleon does not have talent like Snowball and he does not have vision like Snowball. He is a political animal, whereas Snowball was a radical, dedicated to a movement and to a set of ideas. Napoleon's dedication, in the end, is simply to the achievement of power.
Napoleon is an example of how power corrupts. He begins with good intentions (we suppose) but eventually becomes power-hungry and despotic. He is, as previous posters have said, however, very intelligent and ruthless though he eventually succombs to greed and avarice. He is perhaps the embodiment of Orwell's overall argument about the dangers of utopian societies.
Napoleon begins to fall victim to the same character traits that led to Mr. Jones' downfall. He stops thinking about the good of the farm and focuses on his own comfort and vices, particularly drinking. He is the classic example of the oppressed becoming the oppressor.
Napoleon is intelligent but lazy. He is definitely power-hungry. He uses Snowball at first to get the animals working, and he does take advantage of his inventions, but once he is no longer useful he has him run off. One of Napoleon’s best moves was to take the puppies and train them as guards. By the time the animals realized Napoleon had quietly taken over their lives, he was unstoppable. He then became a tyrannical and even lazier leader.