He's a spinoff character, he wont get as much publicity or game sales as Lightning or Cloud.

He wont be more popular...

It's like saying Vincent is more popular than Cloud. It's wrong. And shouldn't be said.

Despite how much more "badass" the character is.

OT: When you think of gaming what do you think of?
One of the things that many people think of is Lara Croft.
Will Lightning ever be anywhere near as big a Lara Croft? No, absolutely not!
And to say she will be bigger than Cloud Strife is ridiculous when her character is heavily inspired by Cloud himself.

I don't think she can surpass Lara Croft in terms of popularity.... literally EVERYONE I know, knows who Lara Croft is, even my grandma @_@

If she had bigger boobs and more female curves... then yes.

Depends on how well is sells in comparison to VII. If it surpasses it, then yes it's very possible. But I doubt it because VII is so popular. Even after ten years, it's still selling pretty well. (Via PSN)

*Warning: Lame Joke Ahead. Do not take it seriously. End Warning*

Since Lightning is supposed to be a new Cloud, AND allegedly it's a woman, fanboys can finally not feel guilty about looking at Cloud and getting an erection, so...

Lightning.

Isn't Lightning just Cloud with boobies?

^ Boobies and a skirt!

I hope so.

Seriously though, Lightning (from what we have seen from the trailers, gameplay videos and the demo) already seems WAY more badass then every other FF main character as of yet (not counting Noctis of course). From handed a bunch of soldiers ass to them to going into hax mode whenever she snaps her fingers to her fighting style in combat, she has so far proven to be more worthy of being the most popular character in the FF series then Cloud. If FF13 sells nearly as much as FF7 did then I believe it will happen.