Another thing is without someone there who has played the games non gamers can have more difficulties. I know Carcassonne was considered too much by my brother and his friends until I sat down and showed them. On their own as guys that just don't play games it was not making sense to them. Having someone who knows what they are doing to show people how the game is played can make all the difference.
I think this is important. Ticket to Ride, D&D, and other geek games have a certain dimension to them that the rulebook can't get across.
For instance, Ticket to Ride could easily look like a dull game. It doesn't click until you really understand how everything works together. You have to see how the economy of cards, scoring, competition for limited routes, planning routes for optimal scoring, and the timing of the end game all combine. The rules don't really do that.
It reminds me of the time I tried teaching a few of my wife's friends how to play Settlers. They refused to do any trades, because they couldn't see how helping someone else would be good for them, even if the trade also helped them. The game turned into a long, drawn out snooze fest.
IME, the line between a "hobby game" (D&D, Eurogames) and other titles is that our games require the players to put effort into them beyond the rules. You have to invest in the world, in your character, or in finding strategies to really get the most out of them. It isn't a simple matter of complexity versus simplicity.
I wonder if their impressions would be different if they were able to watch a video tutorial of the game, with someone explaining how the game works beyond the mechanics of the rules.