I think my loves have already been covered, but I'll try to list them:
Food: Japanese food is superb. From stalls selling rice-crackers to bars selling amazing food (I'm a particular fan of the Doma Doma chain), from Yoshinoya's cheap'n'cheerful to the absurdity of Lotteria, from the underground food city by Kyoto's train station to little hidden ramen basements in Tokyo backstreets. I've yet to have a meal which was sub-standard in any way.
People: The Japanese are polite to strangers. This makes being a temporary gaijin an extremely pleasant experience. My closest major city is London, where getting bruised by other padestrians is a very common occurence. I've only been shoulder-barged by two Japanese in all my travels. I've had total strangers ask in English if I require assistance when I was standing around looking a bit lost - and none of them tried to stab me
(again, a viable concern when you're used to London).
Temples and Shrines: I absolutely adore that you can find these just about anywhere. A tiny gap between shops can lead to a hundred steps which suddenly remove you completely from modern Japan. The architecture and landscape separating these havens from the world are so skilfully designed that you can be in central Tokyo yet have complete peace and quiet. Even children using them as shortcuts to and from school are generally quiet so as not to disturb others. And after a busy day on one's feet, finding a seat is extremely welcome.
Shopping: So much thought and effort goes into some of the simplest household items. You can buy things in Japan which simply do not exist outside that country. Even better, you can buy things in regions of Japan which do not exist elsewhere in the country. Japan has yet to have its cities homogenised by multinational corporations, and even in the busiest places independent stores thrive. It's not just the volume of cute items, although that's certainly a factor.
Public Transportation: Clean, efficient, timely.
Cultural Schizophrenia: Now, I love this about the Japanese. They are a brutal mixture of old and new, traditional and modern, but it
works. From an historical perspective it's easy to see how they make it work, but it's still a joy to experience.
Acceptance: I know, an odd one, but for me I find it refreshing that the Japanese do not belittle other Japanese for liking strange things. I've found middle-aged salarymen in a roleplaying games shop discussing whether or not to buy the latest Vampire expansion. Teenagers mass at Meiji-Jingu to stand around and hopefully get snapped by fashion photographers. Cosplaying is not only acceptable, it's done with love and flair. Little old ladies tap out emails on mobile phones which have so many cute things dangling off them I'm surprised the phone isn't too heavy to lift. People seem a lot freer to express themselves and have fun the way they choose to in Japan (obviously so long as they don't turn up to the office dressed as a maid). I live in a country where to have interests which aren't "normal" gets one a lot of stick.
Vending Machines: Egads, but I love them. I love being able to get a drink without having to hunt down a shop in the middle of nowhere. I love the vending machine in one hotel we stayed at which sold self-heating curry. I love gashapon machines. I love finding machines on lonely street corners which haven't even been vandalised. I love that not all vending machines carry the same range of drinks, snacks, or whatever else it's selling.
Public Toilets: Yes, I love these, too. In the UK most public toilets were closed down during the IRA bombings, and finding one in an emergency isn't easy. Most often you're left to sneak into a McDonald's or a pub and pretend to be a customer whilst running off to abuse their customer-only facilities. In Japan they're damn-near everywhere you would need them to be, they're clean, they're quite often actually stocked with paper even though all guide books say to carry your own, and they're free. I often prefer the squat toilets while in Japan, because I have an odd phobia about loos which flush while I'm sitting on them, which self-flushing ones tend to do, so without going into too much detail it's nice to just relax.
Sumo: Good grief, Sumo tournaments are addictive viewing. It's such a shame that the sport is in decline among young Japanese athletes.
Television: Shimura Zoo is the best TV show ever. The best! I've seen a lady with otter babies she'd rescued who had to teach them to swim. I've seen a cat who loves to be vacuumed. I've seen cats who sit on ticket barriers at small train stations. Words cannot express how much I love this programme.
Nekobukkuro: So, you go to Tokyu Hands in Ikkebukuro, and head up to the 8th floor. There you give a nice man some money, and he lets you in to pet cats for as long as you like. They take homeless cats off the street, give them vetinary care, feed them and give them a home, and let people in to fuss and play with them. They have staff there to ensure the cats are well-treated by visitors. They take cats out of the public area after a couple of hours to ensure the cats get plenty of rest, and bring out fully-rested moggies. The animals are well cared-for, and it was truly heartwarming to see children treating them with respect and gentleness.
Art: I adore sumi-e and other Japanese art forms, and I love the styles that Japanese artists employ. They have a unique artistic heritage which informs even the most modern artist. There are masses of museums across Japan dedicated to art, and each that I've been to has been a pleasure to visit (if, sometimes, a little hard to find).
I don't doubt that there's more, but that's it for now