I wouldn't consider Keisuke a picky eater, but he likes spicy food and sweets (as a treat) the most. He likes curry, soups, and noodles especially.
As for what he dislikes… meat, specifically red meat. It was one of the first things that I knew for sure he was telling me, actually - I was eating red meat and I was overwhelmed with a sense of disgust and repulsion that wasn't mine. It was so intense that I almost stopped eating and had to finish it very slowly. While I still ate meat, I apologized most of the time before starting to eat or I told him to go away so he wouldn't have to deal with me eating it. I don't eat meat at all now, partially because of that and partially because I had been leaning that way for over a decade but didn't have the courage to do it. Some people say that he probably eats fish and, while he hasn't eaten it around me, I'm not completely opposed to him eating fish, but he definitely doesn't eat land animals.
Our tastes are fairly similar, although we're used to different foods. My tastes are more American (both North and South) and Spanish influenced, and his are more Asian (especially, but not exclusively, Japanese). We both like spicy soups the best though! And we both looooove rice, I sometimes use rice noodles but for multiple reasons, rice is pretty much the only starch we eat.
He's a better cook than I am but I'm learning and have improved from where I was last year. He says he likes what I cook but I really want to get to a point where he gets excited when he comes home and smells that curry's for dinner.
For a special occasion, I'd probably just ask what he wanted and I'd make it for him. He does like green curry a lot but I make it for him pretty often anyway, so the special meal would probably be a little different. I might be nice and make udon for him even though I can't eat it. I want to try making daifuku although I haven't yet; I think that's one of the things I want to do this summer. If I wanted to make something I'm more familiar with, I could try making a vegetarian paella but that might be sacrilege, even if I've had some vegan chorizo that's pretty good.