My personal favorites are (board)games which create complexity from
simple rules, for example chess, go or FPSs in the virtual world. A
boardgame which comes close to this ideal is
Carcassonne.
The rules can be explained in less than two minutes and it is great fun!
See below the recording of a nine hour game:
http://www.youtube-nocookie.com/v/UsvNgtBWZeI&hl=en&fs=1&color1=0x234900&color2=0x4e9e00
Don’t be afraid though, that one was played using tiles from 3 sets. A
normal game lasts around 30 minutes. You can [buy the game on
Amazon](http://www.amazon.com/gp/product/
B00005UNAX?ie=
UTF8&tag=hypefree-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=
B00005UNAX)
(disclosure: the link contains my affiliate
ID) or, if you are in
Romania, you should check out
[cutia.ro](http://cutia.ro/Hans-im-Gluck/Regulamente/Carcassonne.html).
Have fun!
PS. There seemed to have been [a site where you could play it
online](http://games.asobrain.com/), but it seems to be offline. There
is [some
speculation](http://answers.yahoo.com/question/index?qid=20090920121644AAQYJmM)
that this is due to copyright violation on the part of the site and/or
due to the site being hacked.