Most board games played by Americans seem as though they can be divided into either pure strategy (e.g., Chess, Go, Cathedral, Stratego) or largely luck-based (e.g., Monopoly, Life, Sorry!, Chutes and Ladders) games. In pure strategy games, player skill dictates virtually the entire game (e.g., a novice chess player will always lose to an expert), which makes the games fun only if players have equal skills. Luck-based games, on the other hand, often have extremely limited strategic decisions (in Monopoly the optimal strategy seems as though it could be summed up as "buy as many properties as you can, trying to get a monopoly, until you run out of money"), skill has very little to do with the outcome of the game, and pretty much everything is based on the roll of a die (or draw of a card). In both types of games, the winner of the game can often be predicted long before the end of the game (and sometimes players can be officially eliminated before the end of the game), which can distract from the fun.
German-style board games seem to have found a very enjoyable middle ground between these two extremes. The games have simple rules (we learned how to play each game in about 10 minutes), don't take too much time to play (30-90 minutes per game), require lots of strategic thinking, yet include enough luck so that everyone has the potential to win the game. For example, we were playing against extremely experienced players, yet we were still able to win a game, and never felt like we had no hope of winning.
The Wikipedia has a good summary of German-style board games; here's their list of characteristics common to German-style board games (taken directly from this page):
- Variable number of players - The games are designed to be played with a wide ranging group. Typically the minimum number of players is only two or three, and the maximum might be four or five or even more.
- Simple, clever rules - The rules for most games are only a few pages and simple to learn. Novel mechanisms that will be unfamiliar to those brought up on older titles are often incorporated. The "roll-and-move" mechanic of games like Monopoly is almost never seen. If a monetary system is included at all, it is usually very simple.
- No player elimination - The games usually continue until some defined set of criteria is met. At that point, a winner is determined. Players don't get kicked out in midgame by running out of money or armies.
- Heavy player interaction - Players often trade, compete for resources, try to win auctions, or affect one another in other ways.
- Minimize direct conflict - War is rarely a theme. It is often difficult or impossible for one player to destroy other players' pieces or position. Usually you are trying to make your own position stronger or stop other players from growing.
- Mitigated luck - The games usually feature some component of luck to keep the games exciting and varied. However, luck is often balanced against numerous strategic and tactical decisions. A skilled player will win far more than a foolish one.
- Diversity of situations - The combination of unusual rules and randomness is used to achieve a variety of possible situations. The goal is to keep the game interesting and fresh even after it has been played many times.
- Modest length - Games are typically designed to take about an hour, and most will rarely take more than two.
- Attractive - Games are usually well illustrated and have quality board and pieces. Bright coloring, and wood or metal components are not unusual. This does often raise the price (typically between US$20 and US$50).
- A greater emphasis on mechanics over theme. For example, US style game designers will reuse the same mechanics but with a new theme (or make use of licensed themes from books or movies) whereas German style designers will more so strive for new mechanics but often reuse the same theme.