In the game Zork the descriptive atmosphere makes the game seem real.  
The games gives you enough information with not overloading with 
unimportant information letting you fill in the details with your mind.  
You know where you are in comparison to your previous location
because of the compass based system and the descriptions of the directions.
Your options for movement vary from room to room. In some rooms you can go
south, north, east, or west others up or down.  You can look at things, jump
 and other various actions depending on the room. In every room it lists 
the directions you are able to move and objects you can react with
helping you to continue into the next room and complete the game.

Myst is made realistic by it's fantastic rendered images.  You can walk 
around the island but you skip from location to location instantly not 
seamlessly.  You remember where you are from your previous direction 
using a map.  In every space you walk through you expect there to be 
items lying around or hints or puzzles somewhere on the screen accessed 
by clicking them.  You can turn in different directions and walk forward.
This makes it seem more realistic to the user.  After entering the library
there are two books both of which contain people trapped inside pleading 
for help to find pages to release them.  This makes you start looking for
the pages and start the game.  There is also set paths that you can not veer 
from  unless it is important to.  

In the Original Legend of Zelda you can walk around the main world to almost
anywhere you please.  You can almost immediately travel to the eighth dungeon if 
you would like to.  You can make your character move up, down, left, and right
on top of the world and when you hit an edge of the screen it takes you to 
another screen that is in that direction.  On each screen you can expect to find
monsters, trees, doors, or other various objects. You can swing a sword or use an
item that you have equipped. the screen has a shift with your character to one side
when you shift screens and your character comes out of the side he was walking from
reminding you of where he was in relation to the last screen.  There are obstacles
that prevent you from going in directions the game doesn't wish you too as well as
puzzles and water preventing you from complete free range.