Dead or Alive: Xtreme Beach Volleyball is a fanservice-loaded video game series that has gotten some female fans, and even a few actual volleyball fans.
Banjo-Kazooie, despite its several innuendos, was designed for children. Still, many adults play it.
Controversially, Conker's Bad Fur Day was initially meant for kids, but saw a sudden change in direction partway through development when critics complained of its similarity to other games of its time. This change in direction involved turning it into a game for adults, while leaving most of the cute graphics intact. Both the box and the game explicitly says "This game is not for anyone under 17". Kids play it anyway.
A great many Kirby fans are people who grew up playing said games. This qualifies because the series in general is and was designed to be for beginners. These people might have moved on in terms of skill but many of them gleefully return for each new installment, no matter how short or easy it is. Sometimes, some surprisingly difficult things can make it in, though (The True Arena, for instance, is certainly no cakewalk). The surprisinglycreepy bosses that some games have may also have something to do with it. Kirby's Epic Yarn also attracted the viewers due to its unique visual presentation.
The Pokémon games are primarily marketed towards children (and were almost exclusively marketed to them early on), yet the series has a large adult fanbase due to childhood nostalgia and the Pokémon themselves and game mechanics having Multiple Demographic Appeal, making it the second best-selling game series of all time next to Super Mario Bros., below. There's also a sizable subset of fans that love playing the game on a competitive level due to the battle mechanics having a surprising amount of depth, whether using the official rules or the ones popularized by the Smogon community. Pokémon's adult fanbase grew to the point that The Pokémon Company now makes frequent, deliberate attempts to cater to them, and some Japanese children unfavorably compare the fanbase with that of Yo-kai Watch due to it allegedly being filled with "old fogeys".
Super Mario Bros., although primarily marketed towards kids (at least for most of its life), has been a big hit with all ages and has become the best-selling game series of all time, with Mario arguably becoming the most recognized game character in the worldnote A poll in the mid 1990's showed that he was more recognizable to children than Mickey Mouse.. It started going for Multiple Demographic Appeal at one point, and was marketed towards casual "non-gamer" audiences as well when it made its move to the Wii.
Is there a museum of Science and Industry or other applied sciences museum near where you live? Does it have any kind of an "interactivity" focus? Was it around in the late 70s? If you search, they probably have a Lunar Lander arcade machine somewhere in there set to free play.note For those not in the know, Lander was a more or less accurate 2D simulation of what landing a Lunar Lander is like, inertia and all, making the museum the periphery demographic here.
Surprisingly, despite skimpy costumes and fanservice, Neptunia has quite a few female fans in the west. After all, clothing or lack of it doesn't make a game good or bad - and women play games too, straight or not.
Most any adult player of Call of Duty, Halo, or any other mainstream, M-rated, online multiplayer FPS will tell you about the curious presence of children and tweens there, who pull no punches in their use of swearing and ethnic slurs. Arguably, the game being rated M - and thus traditionally out of their demographic - constitutes much of the appeal for them.
The Idolmaster is a pop star raising simulation game with an all female cast (That is, until DS and THE iDOLM@STER 2) that was intended for male otaku. However, due to it being very girly, with there being a focus on fashion and the Virtual Paper Doll aspect, songs about girl power, and well, the fact that the cast is all female, there is quite a lot of female fans, especially in the west. Namco even acknowledged this and added three bishonen male idols as rivals in THE iDOLM@STER 2. Unfortunately, while the female fans were pleased, it provoked a massive backlash against the game from the male otaku audience, in part because some of the original cast didn't make it into the sequel and the Bishōnen males were seen to be "replacing" them. Due to the more casual nature, the two mobile games, Cinderella Girls and Million Live, received an even larger female fanbase. Eventually a mobile game called Side M was made, targetted at a female audience. Side M ended up being so popular the servers couldn't handle the traffic at launch.
Team Fortress 2 has a whole following that doesn't care about weapon balance or mini-crits or even, God Forbid, hats. They just love to shipthe all-male castnote Besides some of the background characters, and the mystery of the Pyro together, draw art and write slash fics about them. With in-game achievements like "Beaux And Arrows" (kill a Heavy-Medic duo with the Sniper's longbow), Valve is hardly discouraging this. "I LOVE THIS DOCTOR!"
For exactly the same reasons, the fanbase has a large margin of females as well, despite the Improbably Female Cast.
Heck, there are even children who're fans of the series as well. The most notable are young girls, probably because of the practically all-female cast.
The Periphery Demographics are, in fact, the reason for most of the popularity the series has accumulated. The games themselves are fairly standard Bullet HellShoot Em Ups, however fanartists became obsessed with ZUN's (often conceptually brilliant, always technically flawed) character designs and sought to improve upon them, the doujin communities saw incredible potential in an elaborate setting with piles of Fanfic Fuel, Fanfic Magnets and OC Stand Ins, and the musical arrangers fell in love with the music, to the point where they managed to turn this into this.
Best part of it all is ZUN outright supporting this whole thing by effectively saying "Don't spoil the endings, don't use my sound effects in your fan games. Otherwise, do whatever you want because I don't mind it as it's cool and there will be no copyright issues EVER."
Bully was created to appeal to the fans of the Grand Theft Auto series, but with its high school aged, mostly male cast, it has a very strong following in the Slash Fic writing community. The insane amount of gay jokes and Ho Yay present within the story also contribute to that.
Minecraft. Although official forum traffic tends to strongly imply that Minecraft's primary demographic is male and probably 13-17 years old, there is visible evidence on YouTube and other places, of the game having both a female and adult playerbase as well.
The Sega Mark III (or Master System) was designed primarily to compete with Nintendo's Family Computer (or NES), which was the dominant game console in Japan during the 1980's. While it never took off there, nor in America (due to the stranglehold Nintendo had with third-party developers with their strict licensing policies), it enjoyed great success in Europe and Brazil, where it saw numerous exclusive releases.
Also, for some reason it's extremely popular among people on the autistic spectrum. And no, that's not a joke... the Sonic universe has a pretty heavy amount of World Building to it, and since many of its characters adhere to a homogenized character design (two circles for head and body; stick limbs; just pick a species, add a color and a special ability and you're done), it's easy for people to create their own personas and stick them into the world via fanfiction.
The rather... complicated storylines, the dozens of Mr. Fanservice guys and the buttloads of Ship Tease (either het or Ho Yay, as well as some bits of Les Yay) has made The King of Fightersextremely popular among female players. It does help that it's among the Long Runners, therefore many of the ladies who play it now likely grew up watching other people playing the earlier games.
Guilty Gear also has a sizeable female fanbase for similar reasons.
Catherine has a scene amongst, of all things, competitive gamers, thanks to its versus mode. It's become a staple at some fighting game tournament events, to the point where there are money matches.
The extremely dark and hardcoreMon franchise Shin Megami Tensei has a huge female fanbase, mostly thanks to Persona 3, though interest has quickly expanded to the main series as well. By far the most requested feature in every new Megami Tensei game is simply a female protagonist.
Although Kingdom Hearts is aimed at teenagers and young adults, the series has tons of fans in practically every single demographic imaginable. Two of the most prominent part of its online fandom are probably the Yaoi Fangirls and Disney fans.
Pri Para is a Toyetic arcade game aimed at little girls. Due to the friend card feature encouraging interaction with friends that also play the game, the Virtual Paper Doll aspect (from the makers of Style Savvy!), and just being so damned cute, it has a large amount of adult women that play, affectionately referred to as "Obasan".
It also has a giganticotaku following (both male and female), to the point that most of the official merch is apparently aimed at them.
BioWare games have a strong audience of adult women and non heterosexual gamers, and are very aware of it. David Gaider himself gave an epic dressing-down to a straight male gamer who was offended by the very idea of a Gay Option in Dragon Age: Origins by reminding him that the gaming audience consisted of people who weren't straight, male, or under 35 and that there should be options that reflect that diversity.
The Nancy Drew computer games were developed with the intention of getting younger girls interested in gaming and technology (HerInteractive, the company who makes them, originally had the slogan "For girls who aren't afraid of a mouse.") However, because the series is well-written, designed to be aesthetically beautiful, and just plain good, they've developed several peripheries, including college-age and adult women (who've grown with the series over the past decade,) and a large number of boys and men (many of whom simply like point-and-click adventure games, a genre that's not currently booming.) HerInteractive quickly caught on and changed their slogan to "Dare to Play" in response.
Animal Crossing is targeted at children, but has quite a few forums where most, if not all, of the people on it are mature adults or teenagers. Some fans even remark that the reason the community is mature is because it's meant for children but has no violence, so kids shy away from it.
Super Smash Bros. was meant to be a Mascot Fighter as a last second joke, but it was popular enough with people that they made Melee, which was a competitive paradise. Brawlalienated that demographic somewhat, however. The fourth installment is openly aiming for both groups, with separate game modes called For Fun and For Glory designed to satisfy everyone.
Believe it or not Harvest Moon was originally aimed at a male, or at least neutral, demographic. The first few titles didn't even have female protagonists, or they got shafted compared to the men (in that a game with a female player character would end after they got married). You wouldn't know this by the fandom, which consists mostly of (pre)teen girls and young women. The fact the games have increasingly have Cast Full of Pretty Boys you can marry doesn't help, along with the farming and animal aspects.
There is a Virtual Paper DollH-Game called 3D Custom Girl that, thanks to the program tso2pmd and the ease of modding, is more often used to make Miku Miku Dance models than for its... intended purpose. It's generally a valuable tool to have if you are into MMD.
Kantai Collection was originally designed for a niche military otaku fanbase. However, due to the character designs and the characters' unique personalities, it became one of the most played PC games in Japan. It even have fanbases in countries that Imperial Japan has once occupied, including China.
Splatoon was intended is for young children, but it happens to be very attractive to a young adult demographic, mainly because the character designs have strong similarities to the 90s cartoons they grew up watching. Also, in a rare in-universe example, a song that is at the core of Inkling society actually has Octarian commander DJ Octavio jamming to it.
The SNES Super Scope was almost a failure for Nintendo despite being touted as having laser-accurate controls, and Nintendo dropped the device after a year. It was almost a failure because its laser-accurate controls attracted the attention of the US military, who created a SNES military simulation called M.A.C.S. (Multi-Purpose Arcade Combat Simulator) and a recreation of the M-16 rifle to be used with the simulation.
Undertale is a game that has similarities to EarthBound and is liked by fans from that game, but Undertale also has a huge following from the Furry Fandom; it's not just because it has furry characters in the game, but said characters are written very well and are shown to be very likable whereas furry characters in other games are seen as generic or cliched by most in the furry fandom. The mass amount of fan art, including the rule 34 variations, show just how much furry fans adore the game.
Tekken is aimed at teens and adults, but has a large fanbase with children. This is mainly due to being able to play as animals such as bears and kangaroos, as well as characters like the cyborg ninja Yoshimitsu and the Jack-bots.
Yo-kai Watch is a children's series, and indeed, it's very popular with kids in its homeland of Japan, to the point of baffling adults—indeed, Japanese kids have said they prefer it to the similarPokémon because Pokemon is too popular with adults, and Yokai Watch is uniquely "theirs." Once the series made it to the West, however, it quickly developed a fandom of the same Pokemon-loving young adults.