First off to me anyways Baldur's Gate Shadows of Amn was and is the greatest game of any genre/type to date. Why that is, well because all great things are made up of many small extraordinary things. The Baldur's Gate series has too many great qualities to list here which is why I am going to write a very short, very peculiar, extremely specific list of items that made the game for me during my 15 years of playing it.
1. Joneleth Irenicus the main antagonist voiced perfectly by the incredible David Warner is the most epic villain of any game. Take David's powerful commanding voice complimented by the exquisite writing and you have a MASTERPIECE. Eternity or any other game for that matter WILL NEVER be able to top the character of Jon Irenicus (listen to that name, my god!!) HOWEVER they MUST strive to top him anyways so as to get an antagonist as close to Irenicus' magnificence as possible. Eternity MUST spend the money and hire excellent voice actors, cheaping out will result in garbage dialogues scenes with no depth or emotion. At the same time, having terrible writing will also be VERY unattractive to the player and will also result in RUBBISH. Eternity needs to find the middle ground balancing captivating and compelling writing with seasoned professional actors. I will expect nothing less if they're saying that they want to live up to IE games. Here is my favourite dialogue scene with Jon Irenicus and an example of the middle ground:
"Life... is strength this is not to be contested, it seems logical enough. You live, you affect your world. But is it what you need? You are... different... inside. This woman lives and has strength of a sort. She lost her parents to plague, her husband to war, but she persevered. Her farm has prospered, her name is respected, and her children are fed and safe. She lived as she thought she should. And now, she is dead. Her land will be divided, her children will move on, and she will be forgotten. She lived a "good" life, but she had no power. She was a slave to death. I wonder if you are destined to be forgotten. Will your life fade in the shadow of greater beings?..." http://www.youtube.com/watch?v=r6LbhhoOSIw
2. Music. A game without proper music to intensify the emotion will have NO SOUL to it. Audio is equally if not a tad more important than video. They both go hand in hand playing off of each other. Think of any great game that you've ever played Heroes of Might and Magic 3, Icewind Dale 2, Baldur's Gate's, Age of Wonders 2, what is one component to the greatness of those games? Music, the soundtracks, combat music, dialogue music, all whose purpose is to create and or amplify the emotion being portrayed to the player. Once again money will be the deciding factor to this, Eternity can do it RIGHT and hire a professional orchestra and a composer with video game experience. BONUS POINTS IF THAT COMPOSER DID SOME OF THE IE GAMES. That would be absolutely fantastic and would give it a good transitional bridge feel from the IE games.
3. Depth, which is a very broad and subjective term. In this case depth meaning in game Easter eggs (such as in BGII needing a rouge stone to randomly be able to open a door in the Bridge District which turns out to be a portal.), Books and tomes that have actual stories relating and revealing the world that the player is in, weapons consisting of several pieces spread throughout the game, all the small minute details of the Baldur's Gate series add immense amounts of interest, excitement and depth to the game, which is the goal, keeping players entertained and interested at ALL times.
So in conclusion while graphics, game play mechanics, character development etc... are integral to the creation of a great game, when voice actors, music, and depth are not overlooked, you find yourself with a timeless legendary game.