The 4Kids voice fits Dedede's character very well.....in the anime. In the anime he is presented as a bumbling, illiterate, stupid, and downright mean tyrant who is constantly trying to destroy Kirby. He even looks stupid, with them beady eyes. For some reason, that big bellowing drawl fits that character well.
Dedede in the canon games is very different. For one thing, he looks a lot more likable. He is also not as much of a bad guy. While he is selfish and lazy, he isn't really an idiot, and he doesn't truly hate Kirby. Really, he always ends up with his intentions misunderstood by Kirby or possessed by someone, leading to his beating. Dedede actually seems kind of clever in the games, and he really enjoys his friendly rivalry with Kirby. The 4Kids voice doesn't fit that!
P.S. I can actually picture a Captain Ginyu voice on Dedede! lol. Or some sort of deep, kingly, powerful, voice.