Since I was thinking about the topic, some more details on how happiness works. It's kind of like moodlets in Sims 3. Each happiness effect is boolean, and lasts for a certain time, specifically, a year (at least this is how it worked in older versions). If your dwarf eats in a legendary dining room, he gets some massive bonus that will last for the next year, and get renewed if it happens again during that time. But making it 2x as valuable doesn't help, because it's still the "legendary dining room" effect. Seeing a "tastefully arranged" object is nice because it's a distinct bonus. "Admired own awesome shiny thing" is likewise a distinct bonus, and enjoying mist is neat because--again--distinct bonus (though it's kind of small). Getting Legendary+10 engravers to engrave every surface is nice, but it will only impact room value bonuses; there are lots of other shiny things to get. Having extremely high skill-cooks is also a great boon, because good dishes are morale boosters.
You can assign the dwarf a tomb, which gets room value modifiers, though they won't get the moodlet immediately. And I believe that "admired tastefully arranged" and "admired own tastefully arranged" are different moodlets, so put a nice statue both inside and outside their room.
If you want exact values, there are some
outdated values from 40d at the bottom of this page on the wiki. Though they might still be mostly-accurate numbers.