Something that all men supposedly look good in?
Button down long sleeve shirt and khakis?
Most guys look good in a tuxedo - no, not that powder blue one you wore to the prom - the regular black tuxedo. Helps if it is fitted correctly.
Definitely, tux - it’s used for the same situations too, so it’s a perfect choice.
As the LBD can be worn to more casual events (part of the beauty of the thing) then I would say that blue or black jeans and a black or white T shirt is the male equivalent for those occasions.
Speedos and a mesh tank top.
Bespoke suit.
Tuxedo shirt & blue jeans. Or so I’ve been told…
I was going to say black or navy suit, but tuxedo works, too.
What would it take to get an invitation to your fancy parties? 
Black turtleneck with a charcoal jacket. Can be worn with dress pants or jeans, depending.
Dark suit or tuxedo.
Nice jeans and a long-sleeved white cotton shirt, with the sleeves rolled up a bit. Well, it looked good in the 50’s.
Alan Harper looked good once in jeans and a dark blazer. I think that’s a nice casual look that would work for a lot of guys.
Black leather motorcycle jacket and a Vincent.
The thing about the little black dress is not that all women look good in it, it’s that it’s a basic, versatile clothing item. With the proper accessories, an LBD is appropriate for everything but very casual or very formal occasions. I’d say the closest male equivalent to this is a basic dark suit and white dress shirt.
My thought is the classic blue blazer with gray wool slacks.
A dark (black or navy) blazer/sportcoat is probably the closest thing, as far as being very common and adaptable to different situations. It can look very casual with jeans and a tshirt, more businesslike with khakis, a nice shirt, and a tie, and–in a pinch–more formal with nicer slacks/shirt/tie.
navy blue suit
Another vote for denim jeans and a fitted white shirt. Although, like the little black dress, it’s not every man/woman that looks good in it.
I’m partial to the gray pin-striped suit, which can be made more or less formal based on the shirt and tie chosen. A dark blazer / gray trousers combination is also remarkably versatile. (I do tend to overdress for occasions.)