Computer games are more rigid. Tabletop RPGs are fun (IMO) because of the interactions between people, which more often than not involve modification of the rules. I'm not here to tell people what is fun them, but I'd guess that most people would very quickly (a) decide a computer might as well keep track of the rules - you've reinvented Final Fantasy - or b) look for some friends to enjoy the game you've experimented with by yourself.