Originally Posted by Zenicetus
I like the WoW concept better, where the game world is a huge space shared by all the players, and only the largest and toughest dungeons are instanced. Then you get the best of both worlds -- random interactions and grouping (if you want) with other players, and private dungeons where you're only interacting with a small group.
The random interactions in WoW make the game world feel more alive and "big." I can be in a solo battle where I'm about to be killed by some scary monster, and suddenly another player will appear out of nowhere to help me out. We both wave afterwards, and he rides away. Or I might detour on my travels to help out someone else who is in trouble, or offer to join a quick ad-hoc group to handle a tough encounter. That kind of stuff goes on all the time in WoW. Also there can be world events that everyone shares, like the recent opening of the AQ gates, or holiday events.