I'd say West Africa was screwed over, East Africa equally if not moreso if only because they were better integrated into the Eastern trade, (no good reason for why they shouldn't have been better off OTL) but for whatever reason I don't see any scenario where the Congo and anything south of there to be anything resembling a happy situation.
Maybe that's historical bias, but for the most part you're dealing with insular cultures with very low political sophistication that doesn't fit into a modern state and that would be their only defense against exploitation and abuse from an outside world lusting after their material wealth.
I see what you're saying, but I'm of the opinion that had the colonial system stayed in place a while longer they could have achieved the political sophistication necessary. A lot of African countries today which previously struggled with all sorts of domestic issues are finally starting/have managed to sort themselves out. If they'd been in place under a modern system (i.e. colonialism) for a while longer, I think they would have been able to avoid all the horrible infighting etc that has been plaguing them. There would still be issues, but it could have gone so much better.