The main problem with playing dating sims in general is that the genre as a whole couldn't get more japanese, including almost every single game being in japanese + the whole concept of a dating sim game simply doesn't fly in the west. Having said that, time to answer this question: Anything Key Visual Arts makes comes to mind. Their works are more or less the Platinum Standard of dating sims and visual novels, both in Japan and in the West among fans. The holy trio of games being AIR, Clannad and Kanon. Very emotionally involving, and excellent story-wise. YMMV, of course. Other heavy hitters are Konami (Tokimeki franchise), Aquaplus (ToHeart, Utawarerumono, White Album, Tears/Tiara), Navel (Shuffle!, Soul Link, We Without Wings) and TYPE-MOON (Fate/Stay Night, Tsukihime, Garden of Sinners) -- Fate/Stay Night being bigger than anything in Japan. Also note: some hentai is involved. Often both hentai and non-hentai versions of the same visual novel exist. Surely, many dating sim games from smaller studios (which are many) cater to every fetish one can think of, and as a genre, quality ranges from quick cash grabs to the likes mentioned above. Dating sims are pretty much the only reason the PS2 still sees releases in Japan. As far as western efforts go, I don't really know about those with the exception of one: Katakawa Shoujo, with is very tastefully and well done.