For JAV, I'd like both variety and familiarity, meaning say I'd collect all JULIA as she's the current gen champion tits, Shunka Ayami as hottie/charm queen, Sora Shiina as youth personality with benefits, Asahi Mizuno as desperate housewife, Atomi Shuri as sperm-hungry loli etc. I like to have a bit of every "pattern", kinda. But there's still some "pattern" within my "all patterns":
1. Womanly: not too loli, not too short or tiny body, hair should be longish (at least halfway down her neck, prefer shoulder) & not too practical/boring (Sora Shiina being a counter-example, her short boring hair makes her almost homo-erotic) (Asahi Mizuno is another counter-example, her hair limits her to housewife role for me, if she had more feminine hair she would competes with Julia and Shunka Ayami for all-around hottie). Bit more on hair: a little bit of curl (most likely from hair styling, as typical Japanese hair is straight) is very feminine, but healthy lustrous hair is very important. Dyeing is OK but can kill hair luster, which is very noticeable on HD.
2. sexuality: should not be slutty or cheap in normal situation. But once we get going, should be very comfortable with cocks and sperms and pleasure making for both herself and for her partner(s). This is my main problem with Anri Okita, she looks like a cheap whore even with her street cloths on, and during sex she's too nasty and aggressive.
3. skin: Age's most terrible effect is skin condition. There are quite a few popular mature AV idols that just turn me off due to skin condition (esp. face) that aged poorly. Full-body (no bikini lines) spray-tan, especially semi-permanently is an absolute no. Too white is bad, too black is worse.
4. tits: with some exceptions, cup size should be at least D, we are talking about AV, end of discussion. But it's not purely just mass or volume, the shape matters and recently I start to be more skeptical about a majority of AV idols, their tits might be too perfect (firm) or shape is not totally satisfactory (which ironically could be real). The nipples should be opposite of tits: big heavy tits should have small soft nipples, and A-B cups should have hard erect nipples. Either case areola should not be too small and should swell visibly with stimulation.
5. face: pretty, the two biggest killers is skin condition and eyes (esp. with surgery).
6. figure: the waist, arms, legs all make a difference. Often I get suspicious about fake tits not from just the look of the tits, but how the figure matches the tits.
7. butts: it's so often a disaster zone for AV idols (and tricky for other races too). Too often JAV butts are flat and poorly toned, it's their fucking weird tradition of sitting so much and not letting girls do sports. Same factor makes a lot of young idol's legs fail.
8. pussy: on most CJK girls pubic hair is nice (other races tend to have more problem), and the pussy lips, clitoris also matter, unfortunately most top idols never do uncensored or do it just before retirement. Anyway it would be a big miss if I don't consider the pussy when picking fav girls. I just ask for suppleness in the pussy lips that's mostly enough. To be a superstar, the pussy should be almost but not-quite closed normally with coloration just a tiny bit darker than her thighs and when stimulated the lips expand and redden or darken. The inner lips and clitoris should never be too large or exaggerated.
9. anus: we are really working down the list... the anus should be a bit redder or darker than her skin, and not have a huge "aerola" (rightly or wrongly it suggest the hole is overused). No matter if she does anal or not, a good anus should look inviting. (OT: I had an ex who's white and her pubic hair was epic, reaching her thighs and continues to her anus. Since her I always had an idea for a fantasy porn where I open a hair salon and women would come in for an expensive pubic hair styling. And for an extra, I would shave her anus and throw in a freebie fingering and tonguing too)