Without really qualifying as a stand-alone genre, adult arcade titles could be found in locations all over the world between the late 80's and late 90's. They are actually regular video games that fall into other long-established genres, but are known by all who frequented arcades during this time frame for relying more often on poor quality digitized nude/scantly-clad pictures for an incentive than actual gameplay or audio-visual quality.

Laws and regulations regarding this pseudo genre varied greatly around the world. It's interesting to note the carefree approach most arcade operators took both in North and South America by placing these x-rated cabinets next to regular ones despite the family-oriented environment.

Gals Panic- Arcade	Fantasia - Arcade
Comad's "Fantasia" does a terrible job bootlegging Kaneko's "Gals Panic".

Stricter regulations were enforced in Europe (or Holland at least, where I lived) on the other hand. Arcade locations had a very loomy, dark looking room set up all the way in the back where only adults were allowed. Clearly separated from the main floor by flashing "18+ only" signs and zealous arcade operators, they housed the location's video-poker cabinets, slot machines, and probably their adult titles too. Maybe a testament to the old continent's wiser ways.

It's a fact of life that sex sells. So it seemed natural for money-hungry companies like "Promat" and "Comad" to try to wedge it into the thriving video game market to squeeze out a couple more quarters from us.
On their way to a quick buck they copied or straight-out stealed the code of classics like "Breakout" and "Qix", adding not only the adult content but also swapping out music, replacing sprites, and overall greatly reducing the final product's quality.

Super Qix - Arcade	Perestroika Girls - Arcade
Classic "Super Qix" next to its rip-off: Promat's most decent code-stealing effort "Perestroika Girls".

Targeted titles for this kind of rip-off were always easy-to-pick-up, simpler games. Not only because their structure made the incorporation of erotic content easier, but these genres were also known to target wider male audiences. That's right, male. Good luck finding Jaleco's "Peek-a-boo!" ladies, one of the only nudie arcades that actually contains female-oriented material.
But not all adult titles were bootlegs or rip-offs from questionable developers. You might be surprised to find that companies like Sega, Jaleco and Data East were also involved in pixel-erotica. Most of these attempts are actually quite good (both quality and gameplay-wise), with a few of them even regarded as classics.

So let's get started. Although I'm against any kind of censorship, explicit screenshots have been covered with a small to save myself some headaches and lawsuits from raging parents and upset hosts (hey GoDaddy!). If you want to see the nudies, just fire up MAME.
I also excluded card-based titles, Shanghai-type games, bootlegs, and anything of questionable quality. What's left is a compilation of titles that despite their x-rated content are good games in their own right, or just deserve to be mentioned for one reason or another.

Thanks to:

www.vazcomics.org for many screenshots.
www.vgmuseum.com for a few screenshots.
The guys from the HG101 forums for their contributions.

Block Gal
2 Players	Arcade
Sega 1987

This one will take you back in time. 1987 to be exact. Surprisingly developed by Sega and running on their "System 1" arcade board, "Block Gal" was published by Vic Tokai and designed by Shouichi Yoshikawa. If you can't place him, don't worry. You are not the only one. Despite being the graphic designer for titles like NES' "Black Manta 2", a couple of PCE's "Bonk" games, and a couple of Famicom "Golgo 13" titles, he's largely unknown and a little bit on the weird side. I mean, just check out his website. Half of it still looks like a 1995 Geocities site, he has flash-based games for his cat, his nickname is "Angela", and his female designs closely resemble Macross' "Lynn Minmay".

Shouichi Yoshikawa's art

Block Gal is based on Atari's "Breakout", the classic arcade title where the objective is to control a paddle and bounce a ball around the screen hitting bricks to clear the stage. Unfortunately Taito's "Arkanoid" (which also stole the formula and improved it) did everything Block Gal does and more, one year earlier.
Block Gal suffers from being too simple and in the process ends up being boring. There are literally 4 or 5 different enemies, 2 or 3 power-ups, and only two primitively-drawn manga girls to uncover in the entire game.
Arkanoid's power-up variety made sure the player's progress never stalled when the number of on-screen bricks is low, as trying to hit those last ones before clearing the stage is the most frustrating part of the game.
Block Gal, on the other hand, has a couple of stages that are specially frustrating due to their design. The last couple of bricks are so perfectly protected by surrounding metal columns it once took me four credits to get rid of that last brick.

Shouichi Yoshikawa's art

This is the girl seen walking in Block Gal's title screen (not that we care).

Graphics and music don't help either. The fact that it's a Sega title and its cute/retro anime theme is what attracted me in the first place, but its dated audio-visuals and simpleness don't take it very far. Besides, playing Block Gal does nothing but remind you how good Arkanoid is.

The ladies:
Well... there are only two. Generic and graphically dated. I'm not sure they qualify as erotic pictures, but hey... doesn't the first one look like Lynn Minmay?

No. Despite being listed as "extremely rare" and most likely being the only Sega title that actually has nudity in it, there's nothing else Block Gal can offer that Arkanoid doesn't. A full year before even.

Super Pinball Action
4 Players	Arcade
Tecmo 1991

Four nicely designed old-school tables, a very attractive presentation, and some sexy hand-drawn ladies from the makers of "Dead or Alive". Tecmo's "Super Pinball Action" (totally unrelated to Tehkan's classic "Pinball Action") does a great job simulating pinball machines from the 80's. You know, the ones with LED-looking score displays, before dot-matrix technology was introduced.

Super Action Pinball - Arcade

The game starts with a choice of any of the four available tables: "Carnival" (carnival theme), "Border" (space theme), "Monster" (alien attack theme), and "Sniper" (spy theme). Each offers a correspondingly themed stripper as incentive for clearing common pinball-machine objectives like lighting entire words letter by letter or activating multiball. These tasks are briefly explained in broken Engrish before starting, just complete them multiple times to progressively strip the current girl off her clothes until she's naked or activate the "warp" ramp on every stage to switch tables at will. You won't lose your progress by warping, which is a nice touch, neither are you forced to leave a table when it's completely cleared.
Other classic pinball gameplay features are also included: extra balls, multiballs, multiple flippers, 1 to 4 players games, and even "match" oportunities for an extra credit.

Japanese arcade flyer

But video pinball titles are nothing without a solid physics engine, and Tecmo didn't fall behind. The ball feels heavy compared to other "floatier" pinballs, and giving it the desired direction with the flippers is easy. The infamous "tilt" button is present too.

Super Action Pinball is above all presented in all its charming, nostalgic old-school accuracy. There are lots of visual and audio details that remind of how real arcade pinballs behaved: table lights flashing in sequence when the game is idle, the score display phasing numbers in and out with cool but aged effects, the game pausing when multiball is activated to play a tune and flash its lights before releasing the balls, muffled digitized voices, and other tiny details meant to replicate the real thing. Flashy, noisy, and fun.

The ladies:
It's easy to see the quality Tecmo is known for in present titles like "Dead or Alive" and "Ninja Gaiden" when looking at Super Action Pinball's girls. Although a couple of them have this artificial satanic look in their eyes, their designs are about as polished as you will find in adult-oriented arcades.

Definitely one of the best video pinball arcades. A nostalgic throwback for pinball fans of the 80's and all-around great game for whoever enjoys pinball titles every once in a while.