The most addicting online game?

I play A LOT of online games. You can see the gaming sites I use a lot on my links page. Most really good games get a sequel, but there is one game I have played that has gotten re-made about 4 times... It's Adult Swim's Robot Unicorn.
I think the original is still the best, though. The you are a robot unicorn and you have to break through giant stars and grab small fairy things. Each star is 100 points, each fairy is 10. All you do is jump (arrow up button) and speed up (right arrow button), that's it!
But, the longer you go, the faster you run and the harder it is to see what's coming up ahead of you.
The game ends when you hit a rock or a wall. But... you get three chances. I dare you not to get addicted to this game! (ahh the joys of working weekends.)
Some of my co-workers and e-mail each other back and forth, keeping in mind who has the highest score amongst us and then mock the others when they fail to break our "high score". When we first started playing, the high score was broken just about every day. Now it's broken about once a month, if that. The score gets higher and harder to break.
So, this brings me my question. Have you become addicted to any certain game online? If so, where is and what's your high score? I'll try to break it and let you know what I think of it.
I've found that simple games seem to be the most entertaining and addicting.

The Sims 3 out for consoles

So, I have not bought the game... this is true. However I've been a SIMLOVER since I discovered (the original) SimCity when my dad got it for Christmas one year. Even when the original was an above head view looking down only, I loved the challenge of the game. Building a city, making it prosperous and grow, building roads and then of course the ultimate disaster would strike.. my favorite of course was when Godzilla showed up... who didn't love that?
But, when The Sims came out, I got it for my birthday when I was in high school and have had every addition-- including Sims for DS-- ever since.
I've had at least 4 or 5 expansion packs and watched my old games become obsolete when I upgraded computers, sadly. And then I learned cheats... which I never would have known about had it not been for my husband. I LOVE *MOTHERLODE*! I used it all the time!
Now, I have the Sims3 on our family desktop, but I rarely play it. I love making my character and then making characters of any guy who's ever broken my heart, having him fall in love with me (but not me with him), and then putting him in a pool with no latter to get out or building him into a room with no doors and he dies in there. Which is better than what he would have gotten in real life. Everybody does that right?
But, I don't think I'll be getting Sims3 for the console. It's not because the graphics or bad... I can't comment on them because I haven't seen them. It's because the game has become mundane, at least since the early days of SimCity. There's no surprise in it... they do as I tell them too... or click and instruct them too. There's no surprise monsters, earthquakes or floods. Heck, in the version I have it doesn't even rain or snow. How am I supposed to have a romantic fireside evening with my husband if it doesn't snow?!
EA, don't make it so easy... put some kind of challenge in there! Do you have a suggestion for the creators of the Sims? How would you change it?