World of Warcraft
Ah, WoW. This is my love letter to you. You are crazy beautiful, much maligned, and an icon of geekery.
If you are already familiar with this juggernaut of online gaming, you may be interested in viewing the utterly unimpressive armory profiles of my main characters: Loremaster Rhenn the night elf hunter, Makai the tauren druid, Yanae the draenei shaman, Sahani the human priest, Rakhari the draenei death knight, and Eriss the human mage. (Any sub-80 alts are not included because this list is too large as it is. Okay, except for Ezrah the worgen warrior, because he's a bamf.)
If you are not familiar with the world of Azeroth, allow me the opportunity to pimp, using the magnificent internet dragon macros of Shade. ♥

I think part of the reason some people may be wary of WoW is because of the "war" in Warcraft. They imagine WoW as a neverending battle razing the earth, violent and joyless. But WoW is not a first-person shooter. Sure, you'll do a lot of battling enemies, but you'll do that in Mario Brothers as well. And unlike Mario Brothers, there is much, much more to do in WoW than just stomp turtles. (You can jump on turtles in WoW, it just won't kill them. ;)

You can pick flowers, mine for ore, take up blacksmithing or gemcutting, talk to dragons both good and evil, ride elephants and tigers and raptors, save entire tribes (or decimate them if that's your thing), communicate with the dead, call down blizzards from the sky, tame a wild beast to be your lifelong companion, dance in a tavern while drunk (complete with fuzzy screen and loss of control over your character), explore the depths of hidden cave systems or fly over mountains on your own hippogryph before you jump off and parachute your way to the ground. Visit a crashed spaceship. Become a pirate. Be a walking corpse, an elf, a tiny gnome, a giant bull-man. Go it alone all the way or team up with 20+ other players to take down the most evil monsters that threaten your world. Or, you know, just spend the whole day sitting by a lake with no one around but your pet wolf cub and fish all day in hopes of catching a magical crawdad that grants three wishes.

Don't think of it as World of Warcraft - think of it as Azeroth. Like Earth, there is more going on at any minute than you can imagine.
"Everyone who's seen Avatar, and has appreciated the beauty of that vision... World of Warcraft has been doing it for a long time. Those same visions, those same expansive worlds of color and imagination exist in World of Warcraft as much as it does in a movie. If not better. And the music is orchestral, the music is deep and layered and important." -Jamie Lee Curtis, actor
If you'd like a little bit of visual evidence, I have a YouTube playlist of some of my favourite WoW machinima. Not all of these might be considered the best that WoW machinima creators have to offer (and man, some of them are masters!), but these are some of the ones that I liked, personally.