@Czinczar: I loved being able to go into most of the houses in BG. Also Athkatla, Vizima, Sigil, (Alexandria, Lindblum, Burmecia, Treno, from FF IX) are probably my favorite cities of all time. I love the Athkatla, I just wished it was bigger lol. Every time I looked on the map at all the places you couldn't go in the city it made me sad. Final Fantasy IX's cities are probably my favorite stylized cities of all time. Especially Lindblum and Alexandria. The CG opening for Lindblum is amazing, sadly you can hardly explore anything compared to what the CG video shows.
I always thought a game set in an accurate representation of Water Deep would be awesome.
Anyway exploring a well thought out city truly can make a game just that much better. The Elderscrolls games mostly had crappy cities in my opinion, though MW was my favorite. Dragon Age cities sucked to, I just thought they were trying to pretend that they were big. I would be cool to see perhaps different styles of architecture in different regions.