Imagine you're watching a really good movie and your parents tell you to switch it off halfway through. Wouldn't you be angry? That has nothing to do with addiction.
Of course, the real problem with this statement is video games are much longer than movies. Zelda games can last 50 hours or more, depending on completion and whether you've played the game before or not. It's certainly not healthy to play games like that in a single sitting (this coming from a guy who played Mass Effect 2 in a single 24-hour session).
But the problem is not that you take away their super powers or anything like that, it's a bit more basic: They just want to know how the story ends! With games like Wii Sports and Mario Kart, the "stories" only last a few minutes, at which point it's easy to break away from the game.
Of course, game developers aren't stupid. Most games of the length of Zelda and Final Fantasy aren't written such that they have to be played in one sitting. The real trick, of course, is that you, as a parent, have to be able to find points in the story to switch off the game. This is not something you can do unless you are very familiar with the game itself, so my suggestion is this: Watch your child play the games. You don't have to watch every second; if you have a laptop you could get some work done during battles and puzzles and stuff like that. The point is to follow the story and find the best point to say "okay, that's enough for today" rather than just limiting it to half an hour a day.