I've played a few Japanese-style adventures, H-games, and "dating sims" (ren'ai games) over the years. A few thoughts on some of the games:
Emit series - this is a series of Japanese-style adventure games from Koei that were meant to be used as English teaching aids. The nice thing with these is that you can switch the text back and forth between Japanese and English, good for learning to read Japanese. Decent adventure games in their own right. Released on Saturn and Playstation (and I think SFC).
Roommate 2 - a game where you live with a virtual girl for a week. Made interesting use of the Saturn's clock, so stuff happened in the game in real time.
Doukyusei/Doukyusei II/Kakyusei - these are the games that basically started the whole dating sim genre. Very nice art style from Elf (a little different from most ren'ai games). I think aside from the PC-FX version of Doukyusei 2, all the console ports had the H-portions toned down or removed. I haven't played any of the PC versions, but if I remember right the Saturn versions were yellow label games. The PC-FX of version of Doukyusei 2 was uncut (at least it had more H-scenes than the Saturn version).
Blue Breaker - this is actually more an RPG with some dating sim elements, although the RPG side is kind of weak. I had a lot of difficulty trying to play this game as I couldn't figure out how to "trigger" things in the game story. For PC-FX, Saturn, and PSX.
Tokimeki Memorial/Tokimeki Memorial 2 - yeah, as said earlier in the thread I think where Konami went wrong with this series was in the cel-shaded character designs for part 3. I haven't played part 3 and don't really have an interest in it mainly because the artwork looks terrible. The first two games are classics though, and the second one is just a huge game with less frustrating gameplay than the first. First game available on PC Engine, SFC, Saturn, and PSX. Second game PSX only.
Sakura Taisen series - this is the series I would recommend for people wanting to try out a bishoujo game. Basically an interactive anime with light (very light) dating-sim and strategy RPG elements. Probably has one of the highest budgets of any bishoujo game too, which certainly shows in the end product. Very high production values with excellent visual design, music, and voice acting. The first three games are the best (I have not played part 5 yet). First two games available for Saturn, DC, PC, and PS2 (not sure if ST2 is on PS2 yet). Third game for DC, PC, and PS2. Fourth game for DC and PS2 (I think?). Fifth game is on PS2.
Welcome to Pia Carrot/Can Can Bunny - along with Doukyusei, these are about the only real H-games I've played. As before most of the console ports were toned down (I played the PC-FX versions, which I believe are uncut). The most I can say about these games is that at least they're not the tentacle rape/sex slave type =/
Angelique - basically a dating sim for girls, heh. An interesting game that mixes god game elements (think Populous or Actraiser) with trying to get a happy ending with a bunch of beautiful men (and no, this is not a yaoi game, the central character is a girl). Whether you're a guy who is secure in his sexuality
lol) or female, this is a fun game to play and shows that yes, games of this type can have actual gameplay. There's a whole series of these games, of which I've only played the first (Angelique Special) and the fourth game (Requiem of Heaven, which is an actual RPG).
There's also the "raising" or "bring-up sim" type of game. Princess Maker is probably the most famous example, but I found the PM games to be rather dull (it's very easy to figure out how to raise various stats, at which point every game just becomes a tedious exercise in tweaking stats to get a new ending). However, there is a game on the N64 (!!!) called Wonder Project J-2, that is definitely worth getting for anyone who wants to play a bring-up game. In it you have to guide a robot on her journey to try to become human. Utterly charming throughout with terrific character designs and setting (the game reminds me of a Miyazaki movie).