For Japanese you have your work cut out for you. High end, super high end, shabu shabu, ramen, hidden dive gems, sushi, etc.
Masa, Nobu, Ippudo, Haru, Yama, Kenka, Morimoto, Bond Street, etc...and then you have the unknowns that will knock your socks off. I would suggest trying Morimoto if it's for your GF for the food and possible celebrity chef spotting. Ippudo has killer ramen. Nobu and Masa are the sure fire hits but are $$$. Shabu Tatsu is my pick if you're in the mood for shabu shabu. Curry-ya has some great curry options. Chikalicious for dessert is a must.
Same with pizza. NY style is very low key and a great thing to grab on the go as a quick lunch/snack. Or you can visit one of the old time Italian thin crust spots for great pizza. I am getting fat just thinking about it all!