I am singling out Kaphillica here, but the eroge stigma is as widespread and as silly as mecha stigma, so this is only a sample:

Despite being an eroge adaptation [true tears] is so much different from the rest. Apart from Kyoto animation adaptations of Key games like CLANNAD which I really like, the rest of the eroge adaptation is rubbish. Such examples like the Da Capo series and I was really disappointed with the ending of Akane-iro Somaru Saka. True Tears manages to pull off what others lack a great story, with interesting characters (Noe), which even made some bloggers to become emotional. [...]

The usual pattern is, "all of eroge|mecha is garbage, except for this one series". Usually, as the blogger watches more, another series gains exception status, then another, but the blanket denial continues. It's as if admitting to eroge|mecha producing anything worth the while somehow damages blogger's self-esteem.

Myself, I watched so many outstanding eroge adaptations that I stopped caring for the source material. Often, I cannot tell if something was eroge based. Here's a small sampler of what I can remember to be based on a game with sex (YMMV):

• To Heart: A beloved classic, presented as a collection of heartwarming stories with an emotional climax. Don't miss the omakes! R2 DVDs offer them in brighter video. Spawned derivatives which sucked ferrociously.
• ef ~memo~: The Shinbo take, famous for tugging on heartstrings and SHAFTisms. I think its category at Ani-nouto has the largest number of posts.
• Fate/stay Night: Kicked all sorts of ass, and irritated a huge number of game purists.
• true tears: On the list to watch. Saturnine, Kaphillica, and a thousand of other bloggers agree.
• Kimikiss: This one I sadly failed to complete, but it's famous for splitting the leads, and plotting simultaneously interesting and convoluted. Also, the wide-set eyes.
• Kanon: I hated it on the account of defective characters, but it was enormously popular. Even had a remake! Usually lumped together with Air and CLANNAD.
• Yoakena: Crestent Love does not actually belong with the likes of To Heart and true tears, since it was pretty weak, but Feena was a powerful performance not easily forgotten. Best given a chance without reading blogs about cabbage slash cantelope.