First of all:
this is my first post on this forum and its so cool. How humans love to poke inside the realm of the unknown (chaos i prefer)

Hey dier-erdna I love this question (wink at my name hehehe)
So lets get to business:
Crazy and Insane are first of all both words created by man but the word man means variation. Nobody is the same and nobody picks up the same definitions of a word when taught or just interprets them differently.
Like others said, its all about everyones personal perspective and I think this is true.
these are my thoughts on both words:
Genius: a person with not just a higher level of intelligence, but also much more able to make connections (see patterns, correlations, filtering context, enz) to stuff which i would define as creativity and most importantly.. they have Discipline for whatever scientifical dreams they have. or atleast the combined effect of the three: intelligence, creativity and willpower(discipline) is (much) more promising.
Willpower is very important and dont you forget it. A genius is someone who has a freakylike desire to solve or invent or whatever the discipline is the genius in question is attending to(what his work is). Willpower is the fuel that makes you stick to your dream. the coolest sportscar there is won't be of much use without any fuel (metaphor: catch the moral). I know a genius in real life (again my own judgement but this guy is alpha nerd really amazing). He never wanted to play as a kid because of his own codeset of behaviour. Other people pick to have fun in life, have dirty sex, drink beer all day, become rich or be a boring lawyer. but not this genius oh no. I also think being a genius comes with a prize: a social prize. being a loner because not many will be able to catch up on your mental drifting and because the genius chooses so because he needs to have time to fuel his craving and has no time for smallstuff like catching a movie or going to party. Everyone needs someone to talk to and some stuff cannot be told because nobody understands or there are interpretation errors. But, a genius still has bonds with social order where the mainstream of humans is dwelling: aka the mediocrities, the just another joe's, common herd or whatever label-alike u wish. But I think that they have more trouble explaining their points of view than a social streetkid.
Crazy:
Again just another word/label. My honest opinion is that crazy means asocial. Crazy persons have left the world of human social order completely whatever the reason might be(brain laesion, living in a cave, etc) . Normal people are unable to communicate with the crazy person.
"What the hell is he talking about? what a l00n (crazy). But I saw them, they are all around us and coming!!!" -> One way ticket to an Asylum: Insanity
"Fred: But honey, you said that if i sold my smelly car you would marry me? Angie: I know and I will but you are crazy for doing that Fred

) -> just unorthodox, nor everyday behaviour but still comprehensible in a way or too insignificant to measure up to a room inside an asylum. (why does my neighbour muslim female wear that scarve to cover her face? something to do with religion but thats not too indepth...it's still a bit vague to me)
(sorry for the stupid examples lol but its about the meaning of the example)
But another problem is: Who is capable of making these judgements? How well do you really know the person you are labelling? Are you making those nasty assumtions again?
I think a genius can often be seen as crazy... What if einstein dug too deep? often when a brilliant mind discovers a theory for example it's normal for the rest of the world to accept the theory as true years later the actual discovery. (gah fianlly they see it too, took their time too!) But if he dug too deep it might have caused him to lose himself to chaos and the links to society? Or maybe his discovery is so radical the world isnt ready for it. like when Aristarchus of Samos believed that the Earth went around the Sun the church, in a threatedned position, threw the idea off the table.
My point is: what if a genius drifts off too far? nice to know all that stuff he knows but how to communicate with the rest of the world?
Professor Genius: but i tell you, humans can fly if we remove these genes and replace them with these!. Prof. notsogenius: sure Andy, I think you need a vacation..."
On the other hand: what if einstein, as potent as he might have been, never did a damn thing with his talents? He would just be another guy, forgotten over time
what about tarzan? ;p born in the jungle yeah but he has no social life like the rest of humanity even though he IS human. If he would be magically teleported out of his melodrama and appear at my door and I'd open he would start climbing in the curtains or something... Id be like omg what a crazy fool. But to what extent? Yes everything is relative, a gradient. Even tarzan has a human blueprint of genes and has social skills to a limited extent, underdeveloped id say but animals communicate too. I would understand him better if i knew his background (assuming i dont when i open that door). Assumtions huh. Crazy or just not understood?
To my opinion people always have a choice in judgement. It's easy for me to label tarzan as crazy call an asylum and be done with it just because he climbs in my curtains and that is crazy(unorthodox) but if i knew he is used to swining through the treetops i would be able to link him with monkey behaviour. I wonder how many people see tarzan as a crazy loon or a hero or an excentric man? or maybe all or something else?.. after watching the movie/musical/whatever
So:
A genius to one person might be a crazy fool to another. It depends on the source of judgement but he is still able to communicate with the mass in some extent to present his findings in an orderly manner.
a crazy person cannot communicate with the community in an orderly fashion and is labeled crazy (rightious or not? was the judgement made by someone capable of doing so?)
A genius has part of a crazy person within him(or excentric if you will). I like this but this is my thought: A genius has a hightened level of the innate set of genes together with environmental input determine his intelligence, creativity and willpower.
With the crazy person part I mean chaos to society, uncharted territory if you will but not for himself. He has created his own form of order out of chaos(the great unknown) and is (still) able to communicate his theories to the world (if we consider an invention)
a crazy person to me is someone who has been lost to chaos beyond my understanding.
the behaviour that is interpreted by others is completely out of tune with normal behaviour we compare our perceptions with, maybe normal behaviour of just ourselves.
crazy to me is unorthodox or insane but IF insane i would label it that and not crazy, but insanity is also crazy just a stonger variant of the word.
So crazy to me is more like the gradient between unorthodox(uncommon) up to insane so like: uncommon - crazy - insane
miscommunication in signaling a form of behaviour from the 'crazy'person to the recipient. (flaw as in part of context misunderstood or nonsense to recipient or just a surprise remark etc lalala)
some people label excentric persons as crazy too.
But tbh.. crazy and genius are words i dont use often myself but this would be what I think of both words
Chaos is the daily food for a scientist, they are constantly operating the spinning wheel creating order as we know it from the great unknown chaos.
Anyways hope I put up a reasonable first comment about a subject on these forums and I hope you can use my thoughts on the matter dier-erdna.
Greets, Richie