There are a few different ways to look at this, but what I'm interested in is whether your favorite game is something you first played in your youth, or something you first played as an adult.
So for instance, if your favorite game is something that released when you were a youth but you didn't actually play it until you were an adult, you would pick adult not youth.
Also for the sake of the poll if your favorite game is an updated version of a game you played long ago, choose the option for when you played the earlier version. For example if you played Ocarina of Time as a youth and it became your favorite game and then played Ocarina of Time 3D as an adult and think it is the definitive version, you should still vote youth.
My theory is that, even though we still love new games, most of us have a favorite game from back in the days that just hasn't been surpassed (newer definitive versions aside) in our eyes. We'll see what the poll says.
Are we talking about favorite game in terms of "when I played it I was the most excited" or whatever? Or favorite as in "I like it right now more than any other game in my life?"
Because nostalgia will say Harvest Moon SNES is my favorite game of all time, but if I had the choice between playing that today or some other stuff, I'd pick the other stuff. So it's my favorite "memory" of a favorite game, I guess. Or something.
I have more trouble naming a favorite game, movie, book or author than I used to. Part of it is normal "growing up", I suppose: letting go of stuff you were really into as a kid or teenager, and being exposed to more and more good entertainment so it becomes harder to point to one thing and say "this stands above the rest".
But another big part of it is I'm growing pretty sick of the pandering. It feels like everything I used to like is being copied, bought up, referenced again and again by people trying to cash in on the nostalgia (or just made by people with similar tastes, trying to emulate the works they love). Super Metroid was one of my top games for a long time, but it's not as special as it used to be and not as easy to replay after you've played dozens of games emulating it. Not that they tainted the game for me, it's more that I see less and less of a reason to hold on to it as my favorite game.
Anyway, I guess this means my favorite stuff is now from my adulthood.
@J.K. Riki I guess I was thinking more "at the time" but really everyone defines favorite game in their own way. But I know that I will probably never again play through some of my favorite games (RPGs especially), and there are definitely newer titles I would rather play RIGHT NOW, but that doesn't change the awesome original experience.
I played the Legend of Zelda (NES) first as a youth, although not that much and barely got anywhere playing by myself (mostly watched older kids get farther). It wasn't until I played through it on my own as a quasi-adult (somewhere in my college years) that I really began to appreciate everything about it and see how far ahead it was of other NES games that I had lots of nostalgia for. That said, that nostalgia does exist and it certainly has some effect on my appreciation for it now.
And the lack of nostalgia also affects someone's opinion. As does what your life was like when you were playing a game, the weather outside, even what you had for breakfast. So many factors, but age is certainly a big one in a lot of cases.
@Jargon Ah, okay, I wasn't certain from the wording.
Oh, yeah, I guess I didn't mention my own choices. I separate my faves into "current" and "all-time," so my all-time fave would be Super Smash Brothers Melee, with a close second being Perfect Dark. Smash Bros. has had sequels so I'm sure there's some nostalgia taint there, but shooters have moved into completely different design philosophies than Perfect Dark so there isn't much else like it. The closest would be the TimeSplitters games, which I enjoyed, but the feel was a little different. These were when I was like 15 though, so I played them into adulthood, though I don't really play either anymore. Of course, now that I own a lot more games, I can't keep replaying the old faves if I want to fit in new stuff!
More recently my current fave game was Mario Kart Wii, but I haven't played it much since the Wi-Fi went down, just a little bit of local. So it's effectively been moved to the "all-time" category, but not necessarily through choice. I have a tougher time choosing my current-fave, I guess these things are easier to choose upon reflection. Luigi's Mansion 2 would be a contender, that's been out a while and I still play it now and then. Stuff I got last month like Super Mario Maker could be there, but that isn't enough time to call it yet.
People have mentioned other games that left an impression on me throughout the generations, which I'd count among my faves, just not number one. Super Mario 64 and OoT probably had the most influence on me even if they weren't number one, as they (along with the N64 in general) are what turned games into a hobby for me. I'm surprised no one mentioned Super Mario Bros. 3 though, unless I just didn't see it... that was definitely one of my fave games for a long time as a kid, as I discovered one of my fave things to do in games was to explore and look for secrets, something many NES games didn't offer. I also liked The Legend of Zelda for this reason, of course, and Zelda II. LttP, Chrono Trigger, Earthbound... I'm glad I got to play those back then also.
Youth, definitely. I think it's unavoidable, really. It's easier for a game to make a huge impact on you when it's novel and fresh. As you get older and play more games, that sensation is rarer and rarer.
As for my favorite game, my reflexive answer is the original Metroid. Super Metroid is great, too, but the original struck me like a bolt of lightning. Like, just a quantum leap beyond anything else at the time. But, I dunno. I haven't played it in a while. Then again, I personally judge a game by how much I enjoyed it when I originally played it. Honestly, picking one game is kind of a meaningless distinction. I think seeing a complete list of someone's favorite games would tell you more about them. Otherwise, it'll just boil down to Mario, Zelda, and Metroid most of the time.