I heard Ultima IV was the game that changed the face of RPGs. It's available for free when you sign up for GOG.
Frog Fractions may not be a true text based game, but it has text based section. I tried when I heard about it on Giantbomb and it is hilarious. You can find that for free here: Frog Fractions | Twinbeard Studios
If you were looking forward to a Gremlins 3 and a good Beetlejuice film, I'm sorry in advance.