Before Civilization 4 came out, we were kind of on our own in terms of turn based user interface. I don't want to say that no turn based strategy games came out since GalCiv I back in 2003 but I hadn't played any extensively.
So when Civilization 4 came out, there were a bunch of very innovative user interface tweaks. I also really liked the Civpedia. The Civpedia stores a lot of information that is presented to the user at the time of execution. But there's a lot of good stuff in there that I'm sure users would like to have access to from a single place.
But it always brings up the issue -- if we borrow too much from Civilization 4, would users complain? What many gamers don't realize (and in fact most non-gamers as well) is that the game industry isn't like other industries. Game developers don't *generally* see other games as "competitors". We're all part of the same team -- trying to make good games.
I talked to Soren Johnson about this very issue (designer of Civilization 4). One of the features we wanted to put in was something to indicate that there were no more units to move. In Civilization 4, when you finish moving everything that can be moved, the turn button changes color letting you know that you could press turn and not miss a unit getting its move in. Soren's response was "You shouldn't be afraid to borrow interface elements. If you don't people will just complain!"
I think something as obviously good and logical as color-coding the turn button would be one of those things. It was one of the things Soren suggested we changed based on his beta experience with the game. There were numerous other UI tweaks like this.
In the real time arena, there are certain user interface conventions that have become standard. When games come out and don't make use of them, many gamers (myself included) become frustrated. As much as I enjoy Age of Empires 3, there are a number of UI conventions from Rise of Nations I wish they had borrowed. It would have made Age of Empires 3 a better game.
But I suspect many game designers feel trepidation about borrowing ideas and suggestions from other games. I know I do. I don't have a lot of shame. I believe in the "Great artists steal" but I do feel some shame. I love how you can look at a city in Civilization 4 on the map and see what it's building. We actually tried to do something like that but it didn't work out as well with our UI. After release, I'd like to come up with something like it still for the bonuspak.
Another thing from Civilization 4 I liked (and Soren brought up) was how you can look at a unit and tell if it has moves left. A little green dot appears if the unit has all its moves left. Yellow if it has some moves. And red if it's out of moves. This was another one of those things that I'd like to put in as a bonus pak option. The issue is how to do it cosmetically. In Civ4, you have a fixed camera (unless there's an option I'm not aware of). In GalCiv II, the camera is free form. So we want to make sure what we put in looks okay regardless of the angle and direction.
I think in time many of the innovations in Civ4 will become "Standard" in Turn-based strategy games. If you don't have Civ 4, you can get it here: http://www.civilization4.com.