A common theme in your posts is a big environment with lots of variation - easier said than done of course <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> If you'd have to chose between:
Lots of levels with each level being very different, connected through a map a.k.a. Baldur's Gate or Fallout
One big seamless world with more or less similar graphics throughout the map a.k.a. Oblivion
Less detailed graphics in one big seamless world but with lots of variation a.k.a. World of Warcraft
Which would it be ?