"Die Arbeit ist ihm gelungen"
Are then above comparatives correct? "mehr gelungen" is a pretty frequent term, but the meaning seems to be pretty convertibly.
I don't esteem "mehr gelungen" to be grammatically correct. It's better to use "besser" :) :
Possible, too (with "Arbeit" meaning the work's result):
But the second example is IMO used in written language mostly.
It's possible to use "meister/meiste/meistes" (Superlative of "viel") if you want to say that the work was successful only partly:
But this means that the work wasn't completely successful, so it's less than "Die Arbeit ist ihm gelungen." And it's better to formulate "Ein (großer) Teil der Arbeit ist ihm gelungen" than using "meister/meiste".
The difference is that "gut - besser - am besten" describes the object's overall quality, compared to another object. "viel - mehr - am meisten" denotes quantity.