Gamasutra has posted a three-page interview with Iron Lore's Brian Sullivan about the decisions the team had to make while developing Titan Quest.
"We designed Titan Quest for a global audience, because that is where we are selling the game,) he said. (Europeans tend to like PC games, RPGs, and historical games, and Titan Quest delivers in all three of these areas. Part of why we did a historical and mythological game in the first place was for the European market, because they tend to like this topic. It is also one of the reasons we put Age of Empires in the same setting. When we make any design decision, we think about all markets, but especially America and Europe because they are two biggest markets for this kind of game.)
As for making a name for themselves in the market, Sullivan feels that some of the biggest competition comes from MMOs, not because they are competitors in the genre, but because people simply enjoy playing them so much.
(For retail PC games, I think the biggest problem is World of Warcraft,) Sullivan said. (It is such a compelling MMO game that it sucks up a lot of money and time that would normally be spent on other retail PC games.)