No i see their size is grendizer ( goldorak ) is the same size of grant mazinger but is smaller compare to Mazinkaiser..well a kaiser classe are really big and not push over!, plus i see a episode of Goldorak fight grant mazinger(who a be steal by the enemy) mazinger is a little smaller compare the two of them but if we compare Mazinkaiser is look as child compare to it, many fan mistake the size of goldorak and mazinger's but goldorak is big then the megazord form power rangers who is only 30 meter high but goldorak and grant mazinger are both 40 or 50 high*if not mistake, is long i look it* But Mazinkaiser him is 100 meter high. a real titan!
most sizes i found for mazinger pin him at 18 meters tall, generally making mazinger to be a bit of a shorty among super robots, not that it's weak or anything. while grendizer is about 30 meters tall and great is somewhere in the ball park of 25 meters. most versions of getter robo are taller than that since they're about 33 or so meters tall, except getter 3 since it has no legs and is therefore about 20 or so meters, and original getter robo is the shortest version, both shin getter and getter robo g are over 50 meters tall. mazinkaiser's size seems to gravitate towards 28 meters tall according to SRW, which is where it came from. i personally think that the size of the super robot doesn't really matter most of the time anyway, mazinger z may not be as large as the other super robots, but it still isn't a pushover.