I have both but haven't play Mario Party much. I REALLY like Warioware. It's fun and quick.
My wife and teen sons really like Mario Party. I think it's OK. But because everyone else loves it, it's a great opportunity for the family to play together. And that's a good thing. Our skill levels vary on other games which means some people don't really want to play them. (Everyone's afraid of me when it comes to tennis.
) Mario Party is really just a board game on the TV with some mini games after each round.
I mentioned Mario Strikers Charged earlier. It's one of those games that I get really worked up over. My wife says it doesn't look like I'm having fun even though I am. The controls can take some getting used to, but I've enjoyed learning new levels of complexity & strategy rather than getting frustrated. Ostensibly it's a soccer game, but it has some elements of Smash Brothers that makes it rather entertaining in my book.
Rich
PS why wouldn't my smiley work? [never mind, it did, just not in preview mode!]