League of Legends
Runescape
Combat Arms
Perfect World
Runescape could actually be alot of fun for you guys since it now has a random dungeon that you can sprawl through as a party.
Even though I am kinda old for the game(22), my cousin and I would still go through it because it was actually fun to do as a party.
It is like a Diablo 1 in a sense with regards to the random dungeon of Demonheim(or whatever it is called). Random enemies, random drops, decent random puzzles etc.
I have always had fun with Combat Arms. You level up and all that. There are many game modes: humans vs zombies; deathmatch, team-deathmatch, horde(think left 4 dead), I think there is also a bomb one.
You get more in-game cash for completing matches. Paying for guns gets you slightly better weapons. However, you don't have to buy use any money since if someone purchases the paid weapon and uses it in-game, you can pick it up and use it
.
Perfect World was a good free MMO when I played it all the time. Kinda like WoW but set in mythic China.
I shoulda stayed with it. Seemed like it could have gotten really good. Instead, I bought WoW -_-(which sucks now). Pretty large user base too.
Try out an RTS. Some buds of mine say that their GFs/Wives like to play W3 or Age of Empires.
For consoles:
Baldur's Gate Dark Alliance was always fun to run through with a friend or family member.
Tiger Woods golf games have always been fun with the ladies when I brought them out.
um...Dynasty Warriors games were always fun too.