Achebe is not the only African writer to achieve an international reputation. J.M. Coetzee won the Nobel Prize and his work has been written about fairly widely.
Are you asking about enotes.com specifically? I am always impressed by the great number of African writers that can be found here, along with analysis of their works. In general, though, I agree with you. The west seems to focus on a few token authors from Africa while giving the others short shrift. I suggest you choose a specific African author you are interested in and try typing the name in the search box here on enotes. We do have a page for African poetry though. Here it is: http://www.enotes.com/african-poetry-salem/african-poetry
I can only second the point about modern African writers like Achebe, though it is true that few have attained the type of international acclaim that he has. The issue may be that African writers (except Achebe) are not as widely studied in Western schools as European writers are. Most people that are very familiar with African literature are academics. I think this will change though, as curricula move away from a Euro-centric focus.
I'm not sure who you mean by "we." In this context. I would say that for most of the West, part of the reason for this is that there is not the depth of history of African literature that there is of Western literature. We simply do not have any African literature from any time up to the relatively recent past. I should also note that we do study and analyze African literature today. Writers such as Chinua Achebe are fairly well studied in the West now.