My backlog is huge. I stopped counting a while ago because it was getting kind of depressing seeing the number of games that I had bought, but had done nothing with. I tried all kinds of methods to slow its growth, too. I registered an account at the Backloggery (and then never checked it again), I made myself a deal that I couldn't buy a new game until I had finished at least one of my old ones (which lasted all of six months), and so on. But none of them stuck (sales on digital storefronts are a heckuva thing). The backlog still grows, though more slowly now than it has in a while, thanks to spring and summer being slow times for video game releases, and the number of games I get a year has actually precipitously fallen as my free time gets eaten by things like writing articles for websites.
*ahem*
But, I'm okay with it. I'm okay with building a library of games that I might never play. That curation has become a kind of a meta hobby, and is something that I can engage in to keep me at least on the periphery of the gaming world, even though I don't really have the time to obsess over every game designer's disinterested utterance or new screenshot (now with 27% more speculation!) that makes its way to what passes to game sites these days.
And, since humans are really good at justifying anything, I've laid out a few personal justifications and concessions that I've made to myself to keep the hobby going. These probably won't work for you (because the odds are pretty good that you aren't me), so I can't recommend this to anyone else, though. If you want to build a big ol' backlog yourself, then you're going to have to do your own soul-searching and find out what works for you. Your mileage may vary, caveat emptor, carpe diem, post hoc ergo propter hoc, and so on.
First, and this is probably the most important: don't spend any more than you can afford to. Don't spend the rent or the car payment or the electricity bill on games, even if it's for a super-awesome collector's edition with the gold foil around the case. This can't be stressed enough. And, yes, I know that when you're in a tight spot financially that games can be a good release and escape from the real world, but it's only temporary. Especially when you've purchased a game instead of paying the electric bill. Then you have a new game and no way to play it without running an extension cord to your neighbor's house and stealing some of their power (protip: they get grumpy when you do that). I've been there, and I know this sounds preachy, but it's something that I had to learn the hard way. Besides, even if you don't have a lot of money, there are lots of ways to get your gaming fix (one of the things I did was to make friends with people who had more/different games than I did so that I could play more).
Second: There are enough cheap games out there that you can get a lot of mileage out of. I'm not going to lie, new games can be superfun(tm), and it's kind of neat to be a part of your group of friends and you're all playing the same game and comparing notes over lunch or whatever. But the industry is mature enough now that you can get more games than you could ever play in a lifetime for less than $20 (sometimes a lot less if you are doing the whole digital thing). Some of them are bad, sure (some are even awful or, worse, broken), but finding the gems is kind of rewarding in its own right.
Third: Support the companies you like. There are a few publishers and developers that I like more than others. I'm not going to name them here, since that might sound like a commercial, but I like their games and I want to see them make more, so I throw them some money once in a while on a game or a collectible or something when I can. Sure, I might not be able to play the thing right now (or, maybe ever), but just being able to support companies (especially the smaller ones) is kind of nice, and helping them (indirectly, of course) stay in business give me a better chance of finding something from them that they probably wouldn't have been able to release if they had gone out of business.
Fourth: I have all of the special editions that I need. Special edition games are kind of neat, but they're also kind of expensive. What do you get with them? Usually you get a bunch of digital stuff that you'll probably use once and then forget about, but some other times you'll get branded toys or statuettes or mousepads or pillowcases or whatever that look cool once, and then you have to try to find a place to store them, or worse, pitch them after a few months/years for cluttering up your house. Besides, I can use the money I'm saving by not getting these special editions to buy more regular editions, which look better on my shelves.
Fifth: I like the way that the games look on my shelf. This is kind of selfish, I guess, but I do like the look of a bunch of games organized neatly in a library (I also like the look of a bunch of books organized in a library. See also: magazines, movies, music, and so on. I guess I just like libraries). And, since I have my own house now, I get to decorate it how I want. If that means that I devote an entire wall of my living room to my NES collection, well, then I can do that!
Sixth: Accepting that the games may never be completed. Completing the backlog is a goal that a lot of people have. That's great, and I hope that they make it. However, I've long ago thrown that goal away. Unless I somehow get to the point where I don't have to go to an office and sit in it eight or so hours a day, five or so days a week, 52 0r so weeks a year, then I just won't have time to get to everything I want to get to. But knowing that I can, at any time, find something new and interesting to play, if even for a few minutes. I can rediscover something I forgot was sitting in the back of the backlog, which is a kind of fun in itself.