He's not alive. I mean, he's a genius and all, but face the facts! How could he have escaped when his sister, Suzaku, one thousand some hostages, and everyone on tv was watching?! And then people claim C2 gave him immortality, but she didn't because Lelouch did not kill her. And even if she did, the blood would've retracted back in his body like when Charles shot himself. It was impossible to escape, and there's no way he could've survived. Even I want him to be alive, but he truly isn't. Anyway, what would they do with him alive? Brittania's defeated, and now almost all his friends have turned against him or died. There'd be no story. This is my personal opinion, and I'm not putting up with any crap because I'm the biggest Lelouch fangirl you'll ever see. I'm just a realistic one.

Edit: Okay, so a lot of people claim he's still alive because of the way C2 talked at the end. We've seen her perform a lot of miracles, why can't talking to the dead be one of them? Or, she could've just been talking to herself. You can ask somebody a question even if they aren't there, you know.