There really aren't any leading men/women in hollywood, are there? Chirs Pratt is the closest thing we have to that for males, but even then he wouldn't be considered that at all compared to the leading men 10 years ago. He has potential for it, though.
JLaw is close though. Between AH, HG, and SLP, she's had a big number of critically and commercially successful movies attached to her resume. So I think she's well known enough that she'll add some extra attention to this movie.
Chris Pratt is pretty popular as well, so I think the combo can work.