President Obama's choice of Ghana for the site of his first Presidential visit to sub-Saharan Africa is expressly meant as an incentive to encourage other governments to embrace values this administration is trying to promote around the world. The president is of course well aware of the interest other countries' citizens have in his election, and knows the prestige and legitimacy his visits can confer on the hosting country. Hosting Obama seems a little like hosting an international sporting event, or rock concert, or diplomatic conference.
Going to Ghana may be seen as a slap in the face to Kenya, where many of Obama's relatives live, or other more economically more important countries in Africa, as it is a reward for Ghana's ability to conduct a close election peacefully and lawfully. President Obama made clear in an interview with the Ghanaian Chronicle, that his visit is intended to "highlight the effective governance that they have in place" in that country, and to promote the rule of law, transparency in government, and strong efforts to defeat corruption. The chance to host a future presidential visit might not provide a strong incentive to other governments to clean up their acts, but such an incentive can't hurt.