If I had an unlimited amount of money, resources, and skilled coders/designers, I'd take my shot at creating the world's most realistic survival zombie game. In my opinion, there isn't a good zombie survival game out there that REALLY puts the gamer in the perspective of "Oh crap, there's dozens of zombies in front of me and I have no weapons".
I would do my best to make it the type of game in which it feels so realistic that most of the time you won't be able to successfully kill a zombie, you'll just dismantle it, fend it off, run away from it, slow it down, etc.
I would make it have realistic climate and environmental changes based off of what occurs. I would make the day to night system as realistic as I can, etc. During night your mission would be to find a safe location to survive until the morning, in which you can head out and collect whatever it is you need to survive your next "encounters".
There would be no "special" infected, it would just be zombies. I think that's where a lot of games tend to go wrong. Developers try to add too many things to make it appealing but it goes a tad too far, just my opinion. I'd make it so you actually had to eat, drink and sleep to survive, just like a normal human would in real life.
I'd make it so you would need to be as hygienic as you possibly can, and properly medicate yourself when certain situations occur. If you die before before you find a cure, the game ends and you'll have to restart from the last time you slept. Finding a cure wouldn't be easy, I'd make it something that would take so long you'd want to keep trying for it as if it was a real life goal you're trying to achieve. I want to make it feel like a simulator, not a story based video game itself. As I said, I want to try and make it feel as realistic as possible. If there was a set story for the game, it would get boring quickly and it'd have no replay value.
I would make it so zombies aren't scripted so they don't do everything the same every time in every same area. They would be intelligent at all times. They would hide when necessary in dark locations during the day, and come out of hiding during the night to scavenge intelligently. They would be average human speed, not slow movie-based zombie speed. Their strength is based off of what their strength was previously, before they were zombies.
I WOULD include multiplayer, however, it wouldn't be more than two people. During the game I'd make it so you find a significant other with the same goal that you have. Survive and find a cure. Basically, the game is based off of your choices. If you go to a store in one town and take the Doritos off of the shelf to eat, they won't "respawn" the next day. They're gone, permanently. So obviously you're going to need to travel to MANY locations around the world, not just a few.
I would do my best to make every location in the game as accurate as possible to what it appears to be in real life. Obviously if you attempted to do this the game would never release, because things are always changing. But you can always do your best in creating an accurate depiction.
Damn, I got carried away. Oh well, I actually had fun typing all of that Edited by pjBSOD - 2/22/11 at 2:37am