This cannot be said enough, and should probably be put into the OP: Mini games need to be played more than once! I think Namco did a huge disservice to the game by presenting the first run of each mini game in such a boring and simplistic way. Volleyball practically plays itself, jet skiing race down a straight path, etc. Even the presentation sucks.
Then you visit it a 2nd time and it's totally different. You get a "splash" screen for the activity, allowing you to see all the various control options, select different modes (and each mini-game has a ton of them), and view the game's equivalent to achievement or medals, called silver keys. It's a completionist's wet dream!
For example, the jet ski alone is actually composed of nine courses, 3 for each mode (single lap, multi lap, and going through rings). It's a minor thing, perhaps, but the game is far more deeper than I thought
I'll write up a more detailed hands on later, but man, so far Go Vacation : Mini Game Collections :: Defense Grid : Tower Defense