I wrote a huge post, and then I changed my mind, here's the abbreviated version:
- people liked different games for different reasons over time
- in the mid 80s - early 90s people thought all-out action was fun, now they're seen as "primitive", "for kids" and lacking "depth"
- in the mid 90s - now, people thought epic narrative games with big movies and lots of hours of gameplay were fun
- in the future, social interaction will be the main source of fun, narrative epics will be seen as "too long", "boring", and "nerdy/introverted"
- for example: World of Warcraft, Wii Sports, Pictochat (yeah, I know it's not even a game)
Any type of game can be fun, it just depends on what your interests are. This is why Nintendo is putting out products like Brain Training and Wii Music - the industry relies heavily on sports, fantasy and sci-fi right now, Nintendo is bringing more genres to the people.