Evolver

I never completed it myself but I did get pretty far a couple years ago. The trick was not to play ANYTHING else at the same time as to better adjust to the screwy resolution.

If you want to put gameplay first and are interested in dabbling in some old school eroge, like, REALLY old school there's always Mad-Paradox and Knights of Xentar / Dragon Knight III. Up for a vertical shooter that plays like a slightly erotic version of Fantastic Night Dreams Cotton? Then how about the often forgotten Magic Polalamin? Of course there's also Sentimental Shooting.

Thank you as well, these are just what I was looking for.

Runaway City. I suppose you could say I used it to pull myself back into the genre recently. It may be very, very old but it has always been my favorite eroge (yes, even with that convoluted ending sequence). Now that I've once again experienced my favorite of old, I think it's time to dive into more modern pleasures.