I think, in the case of Leo, it's because he kind of filled in the spot that Johnny Depp and River Phoenix had been in before him: The Teen Idol that 'deep' girls could like.
He didn't take 'light' roles and, in interviews, he could string together a sentence (which put him ahead of people like Joey Lawrence), so the media fawned over him as being the guy who was more than his contemporaries.
He clearly knows how to pick scripts as he's been in some really good stuff over the years, but (and this is just my opinion) his best role was in Revolutionary Road and even then, he was overshadowed by Michael Shannon.
On the subject of Star Wars: I'm not attached to Star Wars as much as others, so I tend to pay the newer stuff no mind...but they did give us Kelly Marie Tran, so they're, by far, the best trilogy!