There were softporn eva games (where you'd see pictures of the characters naked) but that isn't what this is talking about... They're talking about H games that became anime...
After watching Kanon, I can't even see that as having been pornographic at one time... Like, that would be a drastic change... Sorta like the shock of being a Pokemon fan and watching Jocamal (the SNL Pokemon parody as a loose satire of the cigarette industry, but having little to do with pokemon or cigs, as it was... Well, pornographic when it came down to it...) or being a Hamtaro fan and seeing Ebichu... Only worse, because instead of it going from clean to bad, you knew the dirty one came first, and they "cleaned it up"
Along the same lines, Project A-ko may be well known for fanservice, but it started as a hentai project (yuri) but they decided to make it more all ages, so they toned it down drastically... So, the PG-13 a-ko would have been the x-rated A-ko...
The porn industry is quite different in Japan than it is here, which is what allows for things like this to happen there, but not here...
We do have something like that, however... Starship Troopers had a spinoff CG cartoon (Roughnecks) Starship troopers (the movie, anyhow) was definately R rated material (the book most likely could have gotten away with a PG-13 for violence if they had stayed faitfull with an adaptation) Beetlejuice wasn't R rated, but it was definately stratling that PG-13/R fence, and they made a kids cartoon based on it... Dungeons and Dragons was really at the very least PG-13 material, but they made a kids show about it. So, this stuff happens all the time in the US, just never with porn...
As for girlfiend of steel, I'm not sure that was the h one, but sega has always been more lenient with their censorship than sony or nintendo...
Ok... back to wikipedia:
http://en.wikipedia.org/wiki/Girlfriend_Of_Steel
No, girlfriend of steel doesn't look like the H game... the eva h game was a simple collection of undressing pictures, I believe, set to some game like a card game or a board game or something... And it was not authorized by Anno, so he was really upset about it and animerica reported that his retaliation for it was the scene in the beginning of EoE... That shinji represented the eva fans, and gainax who authorized the game without his permission...