An amusement for IF addicts like yours truly is to enter XYZZY or FROBOZZ into every single game,
just to note the response. It is nothing short of stunning to observe how many authors still acknowledge this venerable work.
When you see
hundreds of different people reference to a decades-old computer game, ladies and gentlemen,
then you will know it is a classic.
Amazingly, there is now an online RPG based on the Zork series. I've tried it myself and highly recommend it.
http://legendsofzork.com/