I agree with you on some of the points. I myself find it quite interesting to explore all sorts of places in the game world. Vanguard has a world with vast size and because they did not create "zones" or other unnatural borders to keep players within a certain area, it feels even more wide.

WoW on the other hand side featured a nice compromise between world size and travel options. Classic WoW was kinda huge, especially with the limited travel options we had in the beginning. Unfortunately this has changed since TBC and WotLK. What I am missing most is that there are far less hidden places than in Classic WoW.. and a lot of the exploration feeling has gone because of flying mounts.

I was quite interested in Aion until i started to gather more information about it. It features a "channel-system" like Guild Wars and Age of Conan. This means you are inside some encapsuled zone and not all the players in the same zone are really around you. Also this implies having loading screens or portals / NPCs instead of smooth transitions between the zones.