I've not played Dark Alliance, but I'm not sure what it has to do with crossover for the original games. I'm talking about people who didn't usually play rpgs, playing Baldur's Gate and Final Fantasy 7, even if they never finished them. "Sooo many words! When do I get to shoot someone?!?"
And what did they sell Dragon Age on? How many "spiritual successors" to Baldur's Gate have there been in the past decade? If you don't like the Star Wars analogy, look at it like television, the number of people who watched the Twilight Zone and Star Trek is pretty small (Star Trek was almost cancelled twice), but as the medium expanded, shows like that became touchstones, if not for the audience then for the people making shows, or here, games.
I was agreeing with you about sales volumes when they first released, my point is that being big early has more impact on what follows, now that rpgs and computer games are booming business.
