I would class something like WoW as negative and games like Civilisation as positive, which makes me think it has something to do with where you do the "work". In WoW, the "work" is all in-game, killing monsters for rewards etc. In Civilisation much more of the "work" is done planning your next moves, which is more of an out-of-game activity, meaning you can continue "playing" the game while you do other things.
In the second category . . . well, my choices are going to reveal my age and biases, but here goes. Starcraft, Nethack, and Descent are the big three that have eaten whole years of my life through simply excellent and deep gameplay, so they're my standby examples. Any of the Civ games would count. Deadly Rooms Of Death is a puzzle game that's a genuinely tasty hacker snack. And one of the most direcly addictive games I've ever played was Starscape.
I agree with your distinction between in-game and out-of-game work. Bad games convert time into progress. Good games convert time into skill into progress. Great games convert concerted mental effort into progress.