For the most part I believe in complexity through simplicity. From my own personal experiences it allows and encourages players to formulate deep strategies that wouldn't be possible for a more “complex” game.
Not to say that I don't appreciate depth built into the game, but on that same token no one but hardcore gamers will want to play a game that takes twenty + minutes to set up. Not only is it daunting in and of itself, but it already puts a strike against the game in the eyes of a new player. Again, most experienced gamers won't mind playing an extensive game. I personally don't mind reading multiple rule books and the like, but if there is a better way to make the game more accessible to a wider audience wouldn't it be in the designer's interest to look into it?
My idea of a well made game is one that doesn't make the player feel like they're on auto-pilot. For board games in general I think there is a layer of intimidation that new players will always experience. But when the game starts to feel like everything is happening without much involvement from players there is a problem.
For example, Games like Spades and Chess never have this problem, because there is such a huge amount of strategy behind their relatively simple rules. When I take your Queen I feel way more accomplished than when I play a card that blows up your space station. With no luck or rules involved other than my piece's movement I had to rely on out thinking you instead of waiting for a lucky draw. That's the kind of depth I always shoot for with my personal projects.
Enough of my rambling though. Anyone agrees/disagrees?
I can elaborate more on the games I used. Spades does have a random element in what cards you're dealt but you never have to draw new cards. Even when you're given a bad hand you can destroy your opponents by planning your books and playing a little less aggressively. As for chess, no casual player who's just learning the game is going to go up against a grand master. On that note what I meant in using those two as examples was that when you win in those games it's because you're good at the game and knew how to strategize.
I'm not saying making a game more marketable automatically makes it better. What I'm saying is that games can be simple to understand and offer an oceans level of depth outside of the written rules. That way it could appeal to more players from both worlds.