Well, I think the last time computers played the world chess champion (in 2006), they didn't allow the computer to think on the human time!
And you can always give the computer less time than the human, but this just shows that it's stronger than you and you need to handicap it to have a chance.
Increasing the human time is not an option, since no one wants to watch 8 hour games, and fatigue could also come into play, so the only real option for a winning chance is reducing computer time/power
Correspondence go, similarly, would see fewer errors. Holding a world championship would take quite a bit longer than in chess, though (rough guess: 300-ish half-moves per game versus 100-ish half moves, the latter, I guess, with a bit more variation). That could be problematic, as a world championship in chess already takes years (curiously, some championships finished before the one started a year earlier did)
And you can always give the computer less time than the human, but this just shows that it's stronger than you and you need to handicap it to have a chance.