Wow guys, thanks for the very responsive replies!
After some research, and going through that Japan 2004 guide, this is my preference order of the theme parks within reasonable distance from Tokyo.
Fuji-Q Highland -> LaQua -> Yomiuriland -> Sea Paradise
(I'm not listing Disneyland/Sea cause they are more for sight-seeing rather than thriller rides. I'm more of a adrenaline lover)
Guys, I'm judging based on the pretty outdated 2004 guide, so I would really appreciate if you guys could list out your best 5 thriller theme parks in preference order so I can see which ones are the hot favourites.
Oh ya, and is there any site where I can see more updated photos of Japan theme parks?
(I'll be staying all of my 16 days in Tokyo, so if it's not closeby, do tell me whether it is worth the travelling time and costs)
Oh ya I'll be going from 22nd July till 6th of August, that's less than 2 weeks away!