To get this ball rolling, I nominate Ron Howard.
True, for most of his career he’s made decidedly safe, uninteresting, middlebrow fare. But he also started his career with Night Shift, a witty little paean to the pimp life that features a star-making performance from Michael Keaton.
And I’d also not entirely discount Gung Ho, either.
Joe Johnson. Very lackluster career filled with mediocrity. Yet he managed to direct the superb October Sky, the only film of his that dealt with real people and real issues.
Chris Columbus. His career has yet to match the potential shown in his first film, Adventures in Babysitting (though he did well enough with Harry Potter, it was best he quit the series when he did).
Victor Fleming’s career is pretty uninteresting, but 1939 was his year, as he directed both The Wizard of Oz and Gone with the Wind.
M. Night Shyamalan, if you can identify the gem. I’d lean toward Sixth Sense but wouldn’t push it.
I loved Richard Loncraine’s Richard III, but none of his other films look familiar, and he’s been making films since 1974.
I wonder if George Lucas belongs in this discussion: *American Graffiti *(1973) and Star Wars (1977) both hit their marks with resounding success, I think. His other directorial efforts (I’ve not seen THX 1138) … no.
Joe Johnston. He also directed The Rocketeer, an underrated adventure set in the 1930s and permeated with aviation-y goodness. 
How are you defining “gems” because Ron Howard has a pretty impressive resume as a director:
Frost/Nixon
Cinderella Man (very underrated movie)
Apollo 13
Backdraft
Parenthood
Splash
All good to very good films that make him much better than “lacklustre.”
No props for Home Alone? Yeah…I know. It’s one of my guiltier guilty pleasures.
As far as the ones you’ve listed, I like the majority of them well enough, I guess (excepting Backdraft, which I found to be about as compelling as watching cheese moulder; and Frost/Nixon, which I’ve not yet seen). But none of his films has really grabbed me, or is all that memorable (except for The Da Vinci Code: that’s a bad kind of memorable). Like I said, he makes largely non-threatening fare that the masses tend to find reassuring and pleasant, ergo, they tend to eat his stuff up.
I liked it better when it was called Looney Tunes and Merrie Melodies.
Marty Dibergi with “This is Spinal Tap”. Even though he didn’t film all the concerts where the cocoons worked properly.
Mel Brooks
Bob Clark. 2 Porky’s movies, 2 Baby Geniuses movies, Rhinestone, and…
A Christmas Story.
I think the king of “diamond in the rough” filmmaking is John Boorman who directed both the highly acclaimed cult-movie Deliverance and Excalibur, which is possibly the best re-telling of Arthurian legend yet, but also the utterly incomprehensible Zardoz and The Emerald Forest (which is a bit like Avatar without any special effects or interesting characters), as well as a bunch of other movies I have never even heard of.
Donald Cammell isn’t very well known at all, but lots of sci-fi/horror aficionados remember 1977’s Demon Seed. While that was a pretty good flick (for it’s day), I remember Mr. Cammell as the man who gave the world White Of The Eye, a truly stunning thriller. I’ve had a dubbed copy of this on VHS for close to 20 years now, and I can tell you that the story, the acting, the pacing, the cinematography (man does this film look good!) are all outstanding. This isn’t a movie you forget easily, if at all.
And yet, it had almost no success at the box office, less on video, and today Mr. Cammell and his best movie are largely forgotten.
I came here to post M. Night – he would be the poster child for this thread (I did not see Unbreakable, though). What’s funny (or not) is that after Sixth Sense, Time magazine put him on the cover with the caption “The Next Steven Spielberg” (whom I do not consider lackluster). That said, he writes what he directs, and really, that, to me, is where his movies’ shortcomings are.
Beg to differ (strongly) on the Ron Howard example. Apollo 13 to me is spectacular filmmaking (editing and effects, especially, and that still falls under the director’s guidance, regardless which department did it) and Parenthood really nails head-on the parenting experience and does so with high entertainment value. Some others I’ll give a generous Meh to (Beautiful Mind, Ransom, etc.), but he’s done more good than bad by a long shot. (And YMMV ;))
Ah, but TEF looked amazing.
And I see looking at his IMDB page, he’s involved in a remake of Excalibur and (:eek:) The Wonderful Wizard of Oz. Frankly, I’m not a fan of remakes, and since these 2 movies are pretty much perfect as is, I have to call “bullshit” on the effort. Still, he did make some great flicks back in the day.
John Landis—Animal House, Blues Brothers, An American Werewolf In London—Three of my top 20 movies of all time, but besides these excellent movies, his career has been less than stellar, at least in my opinion…
No, I considered the Rocketeer, but ultimately it falls below Jumanji in his list of films. October Sky, OTOH, is a great little film.
Snowboarder Bo – I agree. Demon Seed is a terrific film.
Kevin Costner, of course. Whether it was to your taste or not, Dances With Wolves was beautifully directed. The rest of his stuff…not so much. (I suspect he had a great cinematographer or director of photography on DWW that he took a lot of advice from…shoulda kept doing that.)