So you are suggesting that my main character eventually changes his personality since he is effected by the environment.
I think this part is correct. For most of the story driven games, you WANT the player's character to have some sort of progression, a growth, a change, something. That, majority of the time, makes the story more engaging and by showing WHAT and HOW this change occurred will get the players to be emotionally attached to the character, more so if they can sympathize with the character's change.
This "new personality" should be reflection of what is "right thing" in contrast to the society today.
This can either be this way or it can totally be the opposite. The character might start with doing things morally/ethically right, but then throughout the game, the outside forces (NPCs and monster killing/jumping/going through puzzles) make him become more in sync with today's society. This all depends on your plot and the character.
I kind of think that games require more of a simple story rather then complex one. How do you make this simple story a hit is using environment, astonishing environment. Shadow of Colossus (with those huge beautiful colossus approaching to you leaves a breath taking scene) as well as Bioshock and God of War used that environment to increase the size and importance of the story as well as attach people emotionally to it. So I think environment in which player plays is equally important to the story. Posted Image
This is true to the certain extent, yes video games can engage players using beautiful graphics. However, a good storytelling within the game can also engage the player. Consider IF (Interactive Fiction). There is no graphics involved, only texts. However some of those stories can be astoundingly engaging, and that comes from the complexity of the story, the deep history and background of the game world (although not a game, Tolkien's Lord of the Rings series pretty much created a whole universe, and is very engaging to the readers).
Basically, it all comes down to good storytelling. I would suggest showing your game story to other close people around you and ask for their opinion. Was it engaging? Was it too hard to understand? Which part did you particularly like/dislike? Where do you think I can improve on? etc.