astonishing, surprising, awe-inspiring, awesome, awful, impressive, awing, jaw-dropping, breathtaking, mazeful, more...

dull, boring, unimpressive, mediocre, lackluster

amazingly, amazingness, amazinglyness, more...

"how !",   very impressive,   great wonderful,   said in awe,   great experience,   wonderful person,   the best thing ever,   beyond great,   it's a knockout,   blows my mind