I have some points such as his usage of literary flair, impact on modern literature..and I am not sure what else to talk about. Can someone help me out and provide advice?
Yes. He perfected a new form of poetry in his sonnets, and while not all of his plays are great he wrote so many and most of them are exceptional. Whether he was one person or not, the wealth of what we call Shakespeare is unequalled.
I'm not sure he's the greatest playwright of all time, but he's certainly someone whose work has stood the test of time and culture and language. His characters and stories are incorporated into the fabric of all things, with such iconic stories as those of the star-crossed lovers Romeo and Juliet, the melancholy Dane Hamlet, and the shrewish Katherine. His language is still in use today in the form of famous lines like "the lady doth protest too much, methinks," though most of us don't even know we're "speaking Shakespeare" when we say such things as "love is blind" or "good riddance." He captures the essence of human nature--which is true for all time and all places--in a language which is estimable and worthy of emulation and study. That makes him one of the greats, for sure.
To be able to write so brilliantly in his time, in such a complex manner of plot and story and moral so much so that his plays have become timeless works of art. I think that's a pretty compelling argument. Plus, the things he writes about in his plays, love, death, jealousy, empire, etc. are part of our everyday lives even centuries later, so his work is consistently relevant over time.
Shakespeare is one of the greatest poets who ever lived simply because he knew what made people tick. Through the beauty of his language, he creates characters from all walks of life who are suffering with universal issues which still plague mankind today--greed, ambition, vanity, sibling rivalry, love, death, illnesses of all kinds, marital strife, marital bliss, a passion for the paranormal, poverty, politics, wealth, humor, insults, happiness, envy, incest, interracial issues, condescending attitudes, murder, and the list goes on and on. You name something you're interested in, and nine out of ten topics will be in Shakespeare's work somewhere. All we have to do as modern readers is get past the "I can't understand it" to "I currently struggle with this language, but I will get it because this is good stuff".
You might receive some debate on this particular subject. I think that a strong case can be made for it to be true, but in the interests of full disclosure, it might be something to be debated. I would say that in favor of the statement would be that much of modern storylines descends from some Shakespearean element. I think that one can trace the modern elements of drama to something or an aspect that Shakespeare developed. Being one of the first writers to conceive of protagonists and characters in full and rich detail, as well as ensuring that all characters featured are round and vivid would be another reason why Shakespeare could be considered to be the greatest writer. He understood before most others the need to present individuals in complex detail as their psychological makeup and motivation reflects this intricacy.