Lucas Black got his shot at leading man status with his Fast and Furious flick, and he didn’t have the charisma, presence, or charm to pass that test the way - say - Chris Hemsworth did in Thor of the first ten minutes of Star Trek.
James McAvoy.
An aside - when talking about people that most people don’t know, could you link to a picture of them? Trying to read this thread, I’m exhausted by the idea of going to google two-thirds of the people listed here. 
I’m always surprised that Julian McMahon hasn’t become a huge leading man - I actually thought being in Premonition with Sandra Bullock right after she won her Oscar would do the trick but I was wrong.
On a different note, someone who would know told me Alicia Silverstone is deeply unpleasant in person, and quite miserable to work with. If true, that would certainly contribute to a lack of success. I think there are very few people that are so fabulous, by Hollywood standards, that they can get away with being miserable. There will always be another blue eyed blond wanna-be, or tall dark and handsome fellow to fill their shoes.
This site seems to say he’s 5’8.
Rounding up, the same site has Cruise at 5’8 and Pacino at 5’7 (and Damon at 5’10).
When I saw Warlock, a cheesy fantasy horror movie in the late 80s, I thought Julian Sands was going to be huge. But he went absolutely nowhere. He ought to have been a pre-Jude Law.
Actually, speaking of Warlock, I expected more from Lori Singer too.
Lucas Black’s IMDB page also has a quote from him about turning down a role because they wanted him to change his accent. It goes something like “I don’t think actors should have to change something about themselves for a role,” or some such. Which, when I think about it, is pretty much the opposite of acting, but there you are.
So it seems he’s pretty unwilling to put on a different accent for a role, which will definitely limit him.
Warlock? Sands played the romantic lead against Helena Bonham Carter in Merchant Ivory’s “A Room With a View.” That should have been a launchoad into the stratosphere of British thespian royalty and at least one meaty scene in Lord of the Rings or Harry Potter plus a story line in “Love, Actually,”
I can’t remember if it’s Mark Kermode or some other critic who expressed this view but someone once commented that the inclusion of Julian Sands in a film was an automatic red flag that the film was terrible. I’m not sufficiently familiar with his career but if this view is more widely held it would explain a lot.
What about Wes Bentley? He was brilliant in American Beauty but then he sort of disappeared for ten years. He had a pretty decent role in the first Hunger Games movie, so thankfully it looks like things are looking up for him, but he just seemed to vanish for ages. I really thought he’d have been a top flight superstar by now.
Christopher Nolan wanted him to be Bruce Wayne in the new Superman vs Batman movie. If he had got his way, nobody would be grumpy about the casting, and Wes would potentially be a box office draw at last.
Wes Bentley got addicted to drugs (eventually heroin) after American Beauty. Drug addiction may explain many derailed Hollywood careers.
How about The Goonies?
Kerri Green - The Goonies, Summer Rental, Lucas… then what?
Josh Brolin - Thought he would be a big star immediately, didn’t really happen until 20 years later.
Jeff Cohen - AKA Chunk - put in a great performance with some his comedic scenes and timing.
American Pie stars Chris Klein and Thomas Ian Nicholas never went on to some of the success almost everyone else did.
Tim Matheson - should have become superstar after Animal House but didn’t
Elias Kotias - Great actor, could have followed in Deniro’s shoes but never that had huge role to cement his career but continues to work steadily.
D.B. Sweeney - great supporting actor, but not known for a one career defining role.
Michael Beck- promising star after The Warriors… then he was in Xanadu…
John Barrowman - great in Torchwood, thought he would be a huge star… not yet, I guess.
Joe Flanigan - lots a bit parts, then Stargate Atlantis, then back to bit parts.
He does a lot of television presenting work in the UK as well as the odd panto but I’m not convinced he’s mainstream leading man material, much as I like him.
(Which reminds me - if you haven’t yet seen “The Five(ish) Doctors Reboot” go seek it out - it’s hilarious, and we discover Barrowman’s dirty little secret.)
Huh? He is the leading man in big budget Hollywood movies. How much bigger do you want? His next two movies he will be playing Professor X in* X-Men: Days of future Past* and Victor Von Frankenstein in* Frankenstein* next to Daniel Radcliff as Igor. It seems like his career is still on the rise.
I wanted to mention Andre Braugher. His career is doing just fine and I’m sure he lives quite well off his steady work. But when I first saw him in Homicide and Glory I figured he would move on to movies and be one of those guys that is always in Oscar contention. He’s still one of my favorite actors.
Clive Owen
He’s playing the main baddie in the “Arrow” TV Show.
Not superstardom, but not starving either.
Not a big career? Leading roles in half a dozen big movies and supporting roles in maybe a dozen more. BAFTA and Golden Globe awards (and an Oscar nomination) for his role in Closer. Many actors would kill for his career.
Agreed. Plus, I understand he narrowly lost the James Bond role when they were replacing Brosnan.
The problem with this thread is that any actor any of us could name for whom the response from everyone else isn’t “Who the hell is that?” already has achieved more than the vast majority of actors. Maybe the people we’re mentioning aren’t “A-list” actors making $20 million per role, but there are just a handful of those.