Oh, this one’s going to be

tremendous
remarkable
great
terrific
enormous
huge
striking
impressive
outstanding
phenomenal
monumental
overwhelming
marvelous
wonderful
sensational
magnificent
superb
superlative
excellent
very good
first-rate
first-class
dazzling
out of this world
breathtaking
fabulous
fab
mega
super
stellar
ace
magic
A1
cracking
cool
wicked
awesome
amazeballs
way-out
def
brilliant
brill
smashing
bosting
bonzer
spiffing
topping
tip-top
top-notch
capital
2.
fanciful
extravagant
extraordinary
irrational
wild
mad
absurd