The Hitchhiker's Guide to the Galaxy

By far the worst text adventure I've played. Infocom games are known for being tough, but this one is just crazy. The puzzles are unbelievably complex and its hard to imagine anyone beating this without cheating.

It's really funny though. You can tell that Adams was involved in writing this game's script. I would actually reccomend playing this if you're a fan of the book, but just accept that you should follow a walkthrough for the entire game.

I personally had more fun with Zork and Trinity, as they were a bit easier and had more expansive worlds to explore. Hitchhikers has a lot of little self contained areas, which is great for variety, but not so much for creating a large world to explore.

By far the most fun text adventure game I've played, in large part because the source material is so funny and easy to remember, but also because it takes huge liberties with making scenarios where you take alternate paths or screw up: Douglas Adams sure put a lot of soul into writing for this game. Of course it's still as hard and sometimes nonsensical as other text adventure games of its time, but it makes up for it by having a really ingenious hints system that acts like a walkthrough which you can activate at any time during the game.

The range of environments and the scenario the game follows is very limited, though, and only covers about half of the first book/radio series. Beating it with a walkthrough is very quick(and navigating the hub world gets grating and boring incredibly fast), but the primary fun of playing Hitchhiker's is to see all the replies of the parser and the various ways you can have fun.

If you've never read/listened/seen Hitchhiker and already hate text adventure games, you'll be hopelessly lost. If you've never played a text adventure before, don't do it until you've tried some other Infocom games(I recommend A Mind Forever Voyaging, Deadline or Starcross), or unless you're a big fan of Hitchhiker.