As with any top XX list of things on the web, this is an opinion.

World of Warcraft
Part of role playing is having your character "just being" as opposed to doing anything exciting. WoW players can definitely relate to that - just ask one how much time they spend logged-in to WoW without having the faintest idea why they don't log off and do something else.

The Sims
The moment when I realized I was addicted to the Sims was the moment when I had trouble getting one of my sim-kids away from his computer games to do his homework. Either that, or when I realized that I was much more concerned about cleaning my sims' houses than my own.

Tetris
Possibly the first truly addictive video game, loved by gamers and non-gamers alike. Tetris just marked its 25th birthday - so to celebrate, we've included a Flash-based Tetris game below.

Final Fantasy VII
I'm not sure the widespread and permanent attraction to FF7 could be called "addiction" so much as "love." All the same, Square-Enix just announced Final Fantasy XIV, and yet most of the franchise's fan base still declares 7 to be the best FF ever. Its popularity led to two sequels and two prequels, including a full-length CGI film. It is the only FF game so often revisited by its creators.

Bubble Bobble

Like Tetris, Bubble Bobble has the attraction of being a quick-fix of fun, and being interesting to non-gamers. This one tests both your planning and perceiving skills, since the ability to imagine the path of a bouncing bubble is the whole key to success. Like Tetris, it has inspired a lot of imitation.