Joystiq - What gives role-playing games their longevity?

I didn't get around to posting Joystiq's regular RPG column last week, which was titled What gived role-playing gamed their longevity?

The strong stories in role-playing games are one major reason for their longevity. Alongside adventure games, RPGs have long been at the forefront of storytelling innovations within the medium. And a story isn't going to become outdated. I may prefer Ultima VII's or Mass Effect 2's interfaces and graphics to Ultima VI and the first Mass Effect, but I find the storytelling more appealing in the chronologically earlier games. Improved technology can't make this obsolete.

RPGs have another strength beyond that: their systems are comprehensible. By this I mean that the mathematical interactions of their internal statistics are usually published in such a way that the player can learn, analyze, and play with them. This is, of course, a manifestation of their roots in tabletop games where everything had to be simple and fast enough to be utilized by people. These systems can thus be weighed against one another, and judged external to technological factors.