I picked up Mario Party for the DS earlier in the week as I needed something for the six hour train journey I had. I'm quite impressed.
There's a good balance of different game types, with a single player adventure, some party / puzzle challenges as well as the straight-up Mario Party. Multiplayer has good (one cart = four players) and bad (no Wifi) points.
The mini games themselves are pretty good, albeit quite easy on normal level. With it being on the train I had to concentrate on those that didn't require voice input, which may well end up being the most fun of the games. I think there is around 80 in total, so I've only seen a few of them more than once.
Definitely one of those games that can be played by the whole family, but has a decent amount of depth and replay value. A 7.5 from me.