I always laugh at these kinds of questions. Why would anyone ever want to be anyone else? Sure you might want their money, or their lovers, or their station in life. Maybe they have opportunities you don't have, or maybe they're more attractive than you. But have you ever really tried to imagine what it would be like to be someone else. I just did, and it wasn't pretty.
I mean, you're so used to being you. I don't want to deal with the way another person's mind works. Chances are he or she would be dumber than me, anyway. I don't want to deal with liking the kinds of foods that person likes or getting used to that person's bowel regularity or irregularity. What if the character likes sardines or mushrooms. Yuck! Maybe the person you admire gets a nasty boil on his or her inner thigh every summer or has relatively harmless kidney stones that cause a pain in his or her side when he or she is stressed. I know what my body and my life brings on a daily basis. I'm too old and set in my ways to get used to a knew existence.
Furthermore, what comes with reincarnation (which I don't believe in, by the way) is a complete rebirth. I wouldn't know I was me being someone else. I'd just be the someone else, a fictitious character with enough conflict and inner turmoil to keep readers interested, and have no idea that this was novel or exciting. I would just be conflicted and full of inner turmoil. Isn't it hard enough to deal with conflict and turmoil knowing yourself like you do, let alone being a whole new somebody with all those problems.
Think about it. At first glance, Franklin the turtle sounds good. I mean, he's got it pretty easy. He lives an old-school life when things were much simpler and all of your friends played nice, and even if they didn't, the learned their lessons in about 12 minutes. But he's just so darn neurotic. I couldn't imagine running around all day thinking just because some animal played with someone else that he doesn't like me anymore or not being able to sleep without my favorite stuffed animal. Wait? But I am an animal. That's just weird.
What about Harry Potter? Magic powers. Admirers all through the wizard kingdom. A cute ginger girl friend. Hogwarts seems like the perfect home. But really think about it. The first time I got anywhere near Volda...oops...he who shall not be named, I would shit my pants ten times. I'm not cut out for wizard duels and confronting certain death at every turn. I can barely handle when a co-worker is mad at me. Nope. Not going to be a wizard.
Even Super Man has kryptonite and a whole slew of villains who want him dead. I'm pretty sure right now there's no one lurking out there, believe it or not, who wants me, specifically, dead. I'm cool that way.
No, I kind of like the gig I got going on for myself. I'd miss my kids too much if I changed into someone else--my biological children and the ones at school--and I'd miss my mind. I'd miss my strengths and my weaknesses. I'd miss knowing just when I was going to have to go to the bathroom each day, and I'd miss the way I could gobble as much pizza I want without feeling full but eat only a little bit of salad and get stomach cramps. I'd miss the way I can make people laugh when they're happy and make them feel like things will be okay when they're upset. I don't know. I'd just miss me.
And who knows. Maybe that character--or person if you want to extend this to real life--that you wish you could be is deep down full of sorrow. Hell, who knows, maybe that nice guy is really a douche bag down deep, and you won't quite be ready to deal with that negative inner monologue. So why envy? Why not just be you?
But if the question were phrased differently, if it read "if you had to be reincarnated into a fictional character, who would it be, then how would I answer?
Mario of course! He's got princesses all over him, relatively innocuous enemies, unlimited lives for the most part, and if things start going wrong, you just press reset. You get impatient--warp zone, and who wouldn't want to have just one day where you could spit fire or ice, double your height with one mushroom, and even fly with one of those cool propellers on your head.
Oh, and that Wild Wing kart is pretty badass. Just sayin.'
This is self-explanatory.