Fun, tasty, cute
The positive comments you make about food, things, activities and shows, plus boring as the let-down.
oishii
polite oishii desudelicious, tasty
おいしい おいしいです
Says food or drink tastes good, at nearly every meal; often a one-word reaction ('oishii!') or the past oishikatta as thanks to the cook.
kore, oishii ne
This is delicious.
これ、おいしいね
kore, oishii desu ne
This is delicious.
これ、おいしいですね
umai is a blunter casual 'tasty' (more common from men, but not male-only) and also means 'good at'; oishii is safe for everyone and the safe choice with desu.
kawaii
polite kawaii desucute, adorable
かわいい かわいいです
A reaction to anything cute or charming (animals, babies, clothes, design, people), used much more widely and freely than English 'cute'.
sono fuku, kawaii ne
That outfit is cute.
その服、かわいいね
sono fuku, kawaii desu ne
That outfit is cute.
その服、かわいいですね
Don't confuse it with kowai (scary): ka-wa-i-i has four beats, ko-wa-i has three. kawaisou is a different word meaning 'poor thing, what a shame', not 'looks cute'.
tanoshii
polite tanoshii desufun, enjoyable
楽しい たのしい 楽しいです
Says an activity or time is fun for the people taking part, most often in the past after an event (tanoshikatta).
kono shigoto, tanoshii ne
This job is fun.
この仕事、楽しいね
kono shigoto wa tanoshii desu ne
This job is fun.
この仕事は楽しいですね
It doesn't mean 'happy': that is ureshii (glad about something).
Learn alongside: omoshiroi, tsumaranai
omoshiroi
polite omoshiroi desuinteresting, funny
面白い おもしろい 面白いです
Says something is interesting or entertaining (shows, ideas, people, places) and also 'funny' (a joke, a person); it is the default praise for content.
kono shigoto, omoshiroi ne
This job is interesting.
この仕事、面白いね
kono shigoto wa omoshiroi desu ne
This job is interesting.
この仕事は面白いですね
tanoshii is about the fun of doing something; omoshiroi is about the thing itself being interesting or entertaining. For a game, show or book, omoshiroi is the normal praise ('it's good').
Learn alongside: tanoshii, tsumaranai
tsumaranai
polite tsumaranai desuboring, dull
つまらない つまらないです
Says something is boring or dull (a show, a job, a person, a day); the opposite of omoshiroi, and in fast speech often tsumannai.
kono shigoto, tsumannai ne
This job is boring.
この仕事、つまんないね
kono shigoto wa tsumaranai desu ne
This job is boring.
この仕事はつまらないですね
The -nai is part of the word, not a negative. Its own negative is tsumaranakunai. Casual speech mostly says tsumannai; use the full tsumaranai with desu.