A few titles you can't go wrong with:
"Wet Summer Days" (especially episode 1)
"Class Reunion Again" (either of the two released episodes will do)
There's also "Virgin Night," which is essentially an animated version of a manga by Yutaka Tanaka.
The best thing about these titles isn't the amount of sex they have, or the fetishes they cater to, but the consensuality of it all. It's BEAUTIFULLY consensual, because it's nice to see couples actually, you know, get to know one another and decide they love another enough to express it in a physically intimate manner. Fancy that, in this age of rampant pornography and promiscuity.