The replay value is what really makes Tunnels of Doom shine. With 99'ers, when you mention "Doom games", they don't think of Doom, the PC game, they think of Tunnels of Doom. That's what kind of mark it made. In particular because it was the only CRPG on the TI for quite awhile.

Before you heavily criticize the graphics, though, remember that this was 1982. The TI was one of the few microcomputers of that era that could display all its potential colors on screen at once, and they seemed to like light backgrounds a lot. And yeah, the controls are obscure, but frankly, Ultima was worse. I remember trying to play Ultima II without the manual, and it got messy pretty quick.

I'm writing my own disk-based CRPG for the TI-99/4a, and posting up a series of articles on my progress with it. I also review a number of other TI games, and related CRPG's that I used for inspiration in the first part. You can read it at http://www.adamantyr.com/crpg