It really depends upon the setting, but as a general rule:
Classic settings: I generally find that the first versions were generally the best, perhaps because they sprung directly from the mind of the creator and were strongly representative of the uniqueness of their imagination. It is not that I didn't like, say, post gray box Realms, but it became something other than Greenwood's Realms - which had a very Greenwoodian flavor.
New settings: Something different. Not simply, "OK, let's do something other than Europe" - because then we get just endless Earth analogues. I'd like to see different approaches all together, which is one of the reasons I like the Magic settings: there's a lot of diversity there, and it isn't only tied to Earth analogues.
But more importantly, I think settings are exactly where you can play with the idea that D&D is different in every world, setting, and table. Not everything in the core rulebooks needs to be shoe-horned into a setting, especially when it doesn't fit thematically. In other words, the rules and lore of D&D as a whole is a toolbox to draw from, but not every project (setting) needs every tool. I dislike the idea that every setting has to follow the same core ethos, or include every element of the rules and lore.