The determining factor in this answer is what kind of games; adult/crazy fun or adult/dignified fun? For the adult/crazy fun game party I would suggest checking out thedrinkingsurvey.com for the Top 15 Best Drinking Games...let the party begin! To host a more dignified party with games I would recommend taking a good look at Entertaining.about.com. This website is by Andrea Campbell author of the books Great games for Great parties and Perfect Party Games.
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One can find a list of card games at the following places such as: Ranker, eZineArticles, Wikibooks, BoardGames, Pagat, Wikipedia and as well as at The House of Cards.
Pet Party can be found on a variety of websites. If you go to Google and type in "Pet Party" it will give you a list of sites with Pet Party on it. See the related links.
There is a link in the related links that has a list of multiplayer online games, both free and paid.
You can download the games at various sites and forums, but I highly suggest you buy the game from a site like J-List. At Touhou Wikis you can find the English Patch for the games.
The best 10 shooting games that are first person shooters are just not PS2 games so what you do it find one you would like from related link list of top selling PS2 games. There will be no new ones that have been released for the PS2 since the list