I think Pa Oki by Zaiko is a true classic. They still play it a lot.
For me the ultimate OK Jazz songs are Infidelité Mado and Bolingo Ya Bougie. I think those are their best composed songs.
And for me the all time congolese rumba song is Nakeyi Abidjan by Nico. That is very well arranged, and mixed. Along with some other songs from that era of his career, like Sanza Zomi Na Mibale, Limbisanga, etc.