Is the lore behind your game such that it still captivates your imagination? Thrall's backstory in WoW – the struggle to free his people from slavery, the fight to establish a new homeland and forge a nation from a handful of different cultures – caught my attention immediately. I know a lot of people criticise WoW for being a Warhammer rip-off (and they may be right) but the game world is so wonderfully realised, that it's hard not to get sucked in.
If you're an RP-er, lore might keep you playing past the point where other players would have jumped ship – simply mulling over the lore might be enough to keep your creative juices flowing. I sometimes wonder if that's a primary reason for Star Wars Galaxies' longevity – is it simply because it's Star Wars? There's at least one generation of gamers for whom Star Wars is an integral part of their identity, so the chance to spend time hunting thugs in the streets of Coronet, or chase Dewbacks in the deserts of Tattooine is too much to pass up.
Maybe you're a little more profit driven. Have you cornered the market for a certain kind of elixir in the Alliance Auction House? Are your blueprints the envy of other players in EVE? While that may seem rather mercenary to some people, there's really nothing inherently wrong with it. Maybe you enjoy playing your part as an enabler in-game; by providing other players with the things they need, you're opening up the game to them. Or maybe you just enjoy fleecing the next mark who stumbles into your corner of the market.
It could be that progression is your thing – you're happiest when you and a group of like-minded individuals are burning your way through end-game content, posting up world first kills, and hurtling towards your guild's sudden but inevitable drama-filled implosion. Still, I'll bet it was fun while it lasted, yes?
I suppose you could be a social animal. if so, you're probably in a large guild, with a friend list packed to capacity, and likely the type of player who enjoys and even seeks out PUGs. You freak. While surly, socially inept, solo players like myself may also be guilded, and have a few solid friends, the way you experience and play the game will lean towards a radically more social style of gaming. For you a PUG won't hold the horrors that it does for the rest of us, but will instead hold the promise of another person to crowd out your contact list. Mind you, with as many friends as you're likely to have, PUGs are probably a thing of the past. Maybe you're not as much of a freak as I thought...
Of course, you may not fit into any of these categories, and are simply playing out of habit now. In fact, you're barely playing any more, and instead are just going through the motions without even trying. You're not playing for fun any more, and you'll barely remember what it felt like to do so. Welcome to burn out.
Fortunately, there are ways around this. The easiest one is to simply take a break. While the developers no doubt bang on about every player being important to them, the sad truth is that one player isn't likely to be missed – the game will still be there when you come back. Unless you were playing Myst Online, in which case I have bad news for you.
You don't even have to stop playing MMOs – just try something different. There are bucketloads of free-to-play MMOs out there. Exteel in particular is a hoot, and while I agree with Turpster that it isn't necessarily an MMO, it's a solid game that's undeniably fun to play – I regularly spend time in there, being blown to smithereens by an array of different players.
Alternatively, stick with the same MMO, roll an alt, and and try the game from a different perspective. I don't really rate this idea too highly though; if you're feeling burnt out with a game, I don't think that going right back to the start will do much more than speed the process.
And, on that slightly depressing note, I must bid you adieu. Hit the comments below and share your thoughts on what keeps us playing – where do you find your fun? I didn't really talk about PvP – maybe the rush facing actual people instead of mediocre AI keeps you logging on? Let us know.