I'm no master writer but I notice that your sentence structure doesn't vary too much. Some of them are rather choppy and break up the flow, which may be the main thing that's bothering you. Don't be afraid to combine sentences and learn to hear what sounds good and flows easily. Also, you aren't consistent with your tenses. Read over a few sentences and you'll notice that it sounds off. If you don't mind, I'll use some of your sentences as examples.
History always remembers the epic, but never the men. The tales always grew bigger in the telling, until one was not sure if it was a fifty foot high dragon defeated with a five foot long sword or a fifty foot long dragon defeated by a five foot high sword.
I would rewrite it as:
History always remembers the epic, but time always distorts the memory of the man. Tales grow more ridiculous with every telling until it's unknown whether it was a fifty foot high dragon defeated with a five foot long sword or a fifty foot long dragon defeated by a five foot high sword.
Notice how I changed a few words and placed emphasis on some of them. IDK if this is better, but that's just how I would write it >_>
There would always be wounded, beaten people. The forgotten faces who were down so far that the workings of the wider world didn't matter. In his starry-eyed youth, Lloyd had once imagined he'd helped these people, too. But his jaded, older self knew better and was ashamed.
Choppy describes this part well. Sometimes short and direct sentences work well, but be careful not to over use them. They get tiring. After a long time, you get bored. Reading them over and over again just gets hard. Do you see what I mean? You want to save these kinds of sentences for ideas you really want to emphasize.
There would always be the wounded, the beaten, the forgotten... the people who the world abandoned long ago. In his stary-eyed youth, Llyod had once imagined that he would be able to help these people rise from their condition. Alas, his jaded, older self knew better than this, and was ashamed of his earlier idealism.
My rewriting of the same idea. IMO, this flows better.
She took a step forward. "If you think for one moment that I'll give Cerberus the time of day for taking away part of my identity, for lying to me and for what they have done in the past you are mistaken. The changes they've made on me are just a measure of control, I know that. And despite how I've changed, there are people willing to stand by my side, even working with Cerberus. Garrus, Chakwas, Joker, they're all with me and fight with me, Kaidan. I...was hoping to convince you to join me. It'd be just like old times."
Let's focus on the dialogue. These are just my stylistic preferences, mind you.
She took a step forward. "If you think for one moment that I'll give Cerberus the time of day for taking away part of my identity, for lying to me and for what they have done in the past, you are mistaken. The changes they've made to me are just a measure of control, I know that. And despite how I've changed, there are people willing to stand by my side, even working with Cerberus! Garrus, Chakwas, Joker... they're all with me and will fight alongside me, Kaidan. I... I was hoping to convince you to join me as well. Think about it; it'd be just like old times."
Periods are so dull. They don't convey that much emotion, as compared to exclamation points and question marks. I mean, I love exclamation points! As opposed to loving exclamation points. Remember that the audience can't hear the exact tone of a piece when it's all text, so you need to give them clues. You get what I'm saying? Keep them engaged with emotion.
But the main thing you should keep in mind is that writing a VN is much more different than other traditional forms of writing. You no longer have to pay so much attention to describing the setting, and you need to focus more on dialogue. It's like writing a play, almost. I'd say you're writing decently, and there's some room for improvement. Still, you're pretty good. Experiment with those other punctuation marks; semi-colons are a favorite of mine
As are exclamation points! Question marks are cool too, don't you agree? Colons: the thing following it doesn't even need to be a sentence. Just play around with your keyboard and vary your sentence structure.
For reference, here's a handy-dandy website with grammar rules
. I use this site all the time and it's trustworthy. Sometimes there's a pop-up, so just click out of it and you can pretty much relive your English classes >_>