Although Borderlands was just released in late 2009, I feel comfortable including it on this list as it has received great reviews and is quickly becoming one of my favorites. Although it is arguable whether this is an RPG or an FPS, I'd classify it as the former because the essence of this game is its role-playing functions: completing missions, attaining better weapons, armor, and mods, and improving character skills. You get to choose between four characters (Soldier, Siren, Hunter, and Beserker), but with the endless number of guns, class mods, grenade mods, and skill tree combinations, no two characters are really alike.
As a multiplayer LAN game, this game is fantastic for four friends who want to do missions together, do arena battles, and just explore Pandora together. You can utilize a party chat feature to talk to one another while you're playing, which is very helpful. Once all of the missions are completed, you begin a 2nd playthough in which all of the missions restart, but the skags and bandits begin at level 34. There is also a 3rd playthrough, so there are many hours of gameplay and fun.