None of his offence looks that great, but he jumps high doing it. Also, after Shelton left, he sort of fell into the role of "guy who does that one crazy spot at the Rumble".
I guess a lot of people dislike Kofi because he's had numerous mid-card title reigns, while others never seem to be given half as much of a chance. Really, though, it's because he got over early, has a catchphrase the crowd can join in on and his popularity with crowds doesn't seem in anyway affected by the lack of effort creative put into him and his character - in other words, he's the perfect WWE mid-carder.