Answer by Japanese teacher
(1) うまい umai delicious
This is a relatively casual expression commonly used by males and preferably among friends. If you are attending a dinner with your superior and you wanted to tell him/her that the dinner is delicious, use oishii instead of umai.
(2) 最高 saikoo best
When you say your meal is saikoo desune, you are giving it the best compliment because it’s the best.
(3) 絶品 zeppin superb, excellent
Zeppin literally means “an item of unrivalled quality”. When you are so delighted with your meal that you don’t know what else to say, going with zeppin desune would never go wrong.