They screwed up big time on Mass Effect 3. Check this,
What if, the only way to destroy the Reapers is to be able to communicate with them, to hack into their cybernetic minds and shut them down from the inside... but that would require you to have reaper tech on your brain. To save the galaxy, Shepard goes through indoctrination. (This could happen in the beggining of ME3). His body is partially deformed, metal cables and leds visible through his now pale skin. His voice changes and his eyes glow. Big chance for good dialogue: crewmembers dont trust him anymore, Ashley may leave the crew if you dont convince her to stay and that you're not insane. The person you had romance with previously is afraid of you now. She or he says you're not the same anymore. Shepard (and the player) feels lonely for the first time in the trilogy, but he knows he's the only one that can pull this mission off. He knows he's doing the right thing, even if that requires sacrificing himself. But now that he has Reaper tech on his body... he can communicate with them. They talk to him. They explain their motives. The lines between paragon and renegade become blurry - it doesnt make any sense anymore. Maybe they're right. Maybe everyone should submit to the Reapers if they really are unstoppable - doing so would just avoid bloodshed and war. Wait, no! You cant give up Shepard! We have to save the galaxy...! Meanwhile, Illusive Man hires his space ninja guy, Kai Leng, to assassinate Shepard. But he cant do it alone. Kai Leng must travel through the galaxy, following a list of dossiers and recruiting people to help him in the battle against Shepard... Exactly like you did, during Mass Effect 1, when fighting against Saren. It all makes sense now. During the climax of the game, there's a huge battle between the two ships - all the crewmembers you failed to convince that you're not insane, have left you or joined Kai Leng's side. While both spaceships are engaged in a space dogfight, Kai Leng teleports to inside your ship as soon as your shields are down... and you two have a final showdown inside the very Normandy. This isnt a battle for survival anymore - its a battle to save the galaxy but also to prove everyone you're not the same insane monster Saren was. Or is this exactly what Saren was thinking, when you killed him? Leng perishes and Shepard survives thanks to his reaper body augmentations (crewmembers die during the battle kind of like in ME2 suicide mission, depending on certain decisions).
In the end, you must meet the Reapers alone (or everyone else will be indoctrinated too), so Shepard is left alone talking to the Reapers in a strange, surreal scene (maybe he's floating in space and the Reapers are around him, judging him, talking through his mind). Reapers explain that, as robots, they are unable to design things that they werent programmed to do. So they rely on allowing organic life to develop, to then study their technology and improve their own with it. And then they exterminate them and use their broken souls as fuel before they develop too much and threaten the Reapers - and that has happened for countless eons. They also mention how every living being, came from their seeds - a tiny bit of their biomechanical DNA. However, they offer Shepard a chance - he may integrate with them, becoming a Reaper, and helping them wipe the galaxy out. Shepard never really had a choice - he was destined for this. The player loses control (in panic) as he witnesses Shepard opening his arms and allowing a Reaper to absorb him. There is nothing the player can do. Shepard is now inside it, part of it, an organ, a gear - just part of a much bigger system. (His arms are wide open, connected to the Reaper biomechanical systems, in a HR Giger fashion and Christ-like pose). Flashbacks of every important conversation of the trilogy go through his mind, as Shepard, minutes before complete assimilation, remembers his job. He may give up now and become part of them, or he may struggle. Two endings may ensue:
- Good ending happens, if you did good things throughout the trilogy. Shepard remembers saving the Rachni Queen, not killing the infected Thorians, worrying and saving his crew on Mass Effect 2. He remembers his crewmembers - no, his friends, and his love. He has to finish the job... for them!! In a last burst of willpower, he takes over the Reaper with his mind. Their systems, as robots, were designed at least to an extent to have an operator, perhaps used by their creator eons ago. And now its used against them, as Shepard controls them for just a few moments. He knows he cant keep up for too long (or it will destroy his mind), so he dominates all Reapers and forces them to dive into the Sun. Shepard knows that if he stays, the Reaper will retake control of its own systems and may even control him. He cant take the chances. He knows that there is only one way out, only one way to make sure the galaxy will be safe. Game ends with Shepard diving into the sun too, the reaper technology melting into its most basic chemical forms. Ashes to ashes.
- Bad ending happens, if you were ruthless or selfish. You remember killing all those people in cold blood, just means to an end. You were just a guy, doing your job. Saren was weak. They were all weak. But you're not. You're part of a Reaper now. You are the all-knowing, inevitable end. You are an immortal death bringer. You failed your mission and now your friends must die. But its okay. Its all means to an end. Game ends with the Galaxy being wiped out, only primitive lifeforms survive. The cycle continues, forever.
This would make Mass Effect 3 a game about discovering who are you, truly - after Shepard was indoctrinated, did he remain the same? Would you remain the same? To what extent are you affected by your past? Its a journey of self-understanding, of rejection (from the crewmembers) and finding out your true purpose (in the end). Its also about the origin of the galaxy (the Reapers being the creators of every organic life) - about man, meeting God, meeting his Creator. What if God wasnt a nice guy? Would you stop him, or would you join him, if you had a chance? Also, another point: You becoming what Saren was, without noticing. Do we really have control over our lives, or was Shepard destined for this, just like Saren never had a choice?
How's that, artistic enough? Excuse any typos, i'm drunk.