Dragon Ball Budokai series - obviously a great game to just get some Arcade fighting in, hopefully Sparking Zero is just as good! 
	 
	League of Legends - Oh boy, how many hours I have spent!  
	 
	Mario games in general, I think this one is self explanatory
 
	(sorry to be more broad, but, Nintendo games in general are usually based around playing with others. I think one of the best examples is Wii Sports. The gimme of a game that everyone with a Wii had, hold some of the best time with friends.)
 
	And who could forget Guitar Hero.... Who doesnt want to be apart of a band with the homies!