Extreme inequality is certainly not unique to Nigeria, but this report, which aired on the PBS NewsHour a couple of nights ago, vividly depicts the economic disparities in Lagos. It's part of a series on Nigeria that is exactly the sort of thing public television should be doing.* Note, incidentally, Bill Clinton's appearance toward the end in the section on Eko Atlantic City.
(*I watched it online, as I don't have a working TV setup, as I've mentioned before.)
ETA: As discussed in the comment thread, the issue is not inequality per se, but rather the failure to meet the basic needs of a large portion of the population despite economic growth.