When we all learned that Superman and Wonder Woman were dating — or at least, boinking — the reaction was almost entirely negative. And for good reason: this diminishes Wonder Woman somewhat, by turning her into Superman's New Girlfriend. But the truth is, superheroes dating each other is almost never a great idea. I can count on the fingers of one hand the number of times a romance between two superheroes has been cool.*
Here's why superheroes should date normal people instead of other supers.
First off, let's get one thing sorted out — we love superhero romances. Superhero comics are basically soap operas with more fight scenes and zany costumes, and this means that romance is a key ingredient. Superheroic characters don't just need action and high-powered fisticuffs, they also need heartbreak. And the number one source heartbreak is romance. (With families coming a close second, probably.)
A lot of my favorite Incredible Hulk stories have to do with Bruce and Betty almost getting together but not quite making it, or getting together and running into trouble. Who can forget that great issue during Peter David's run, where Bruce is running to catch the train that Betty is on, and he just misses it, but then she jumps off the train and meets him? Likewise, a lot of my favorite Superman moments revolve around him and Lois, and many of the coolest Spider-Man moments involve Gwen Stacy or Mary Jane Watson.
So yes, every superhero should have a love interest — it's just part of the genre. In fact, I'd argue that Wonder Woman's lack of a compelling love interest is as much a problem for her character, in the modern age, as her lack of a great rogues gallery. Jodi Picoult and Gail Simone tried to give Wonder Woman a love interest, Nemesis, and it totally didn't click. Although at least there were some fun scenes of Diana showing how Amazons court someone. And of course, there have been plenty of incredibly awkward superhero romances over the years.
But superheroes' love interests shouldn't be other superheroes. In general. There are bound to be a few exceptions to this rule, and I'm happy to hear them in the comments. Like, maybe the Scott Summers/Jean Grey relationship is an example of a love affair between two supers that worked, for a while. But in general, superhero romances work better when the love interest is not superpowered.
For one thing, superheroes always need stuff to anchor them to the real world. A lot of that usually comes from their non-superpowered supporting casts, including friends and people they work with in their secret identities, or whatever. Or roommates, or family members. But a non-superpowered love interest can be a powerful factor keeping the hero anchored in the real world — and given how easy it is for superheroes to just slip away into a land of nonstop fights and random plot devices, the more help they can get staying anchored in reality, the better.
For another, the relationships between superheroes are based on a lot of other stuff, which is worth exploring and which romance would likely crowd out. When two superheroes team up, you get to explore issues of comradeship and teamwork. You get to see heroes be friends with each other, and you get to see friends disagreeing over stuff. A lot of the richest superhero storytelling comes from team-ups and sometimes uneasy cooperation, and it's hard to cover all that ground if the heroes are also dealing with their lover's quarrels and stuff.
Just imagine how the famous "Wonder Woman snaps Max Lord's neck to stop Max controlling Superman" storyline would have gone if Wonder Woman had been dating Superman at the time — it would have been a relationship spat, instead of a serious ethical question.
There's also the issue that people have been bringing up with Wonder Woman — that if a more famous male superhero starts dating a female superhero, she's likely to be pigeonholed as just "Superman's girlfriend." It's hard enough for female superheroes to get enough exposure and carve out their own identities — given how many of the most prominent ones are still female versions of existing male characters. In an ideal world, neither party to a romance would become defined by it — but in superhero comics and media generally, we're not there yet.
(The worst super/super romance, for my money? Batman and Catwoman. I've never understood those two as a couple, and they've given rise to some of the most idiotic storylines in comics, like when Bruce sees a cat-shaped stalagmite in the Batcave and decides this means he's destined to be with her. And the more recent shenanigans. I get Bruce/Talia, but I don't get Bruce/Selina. At all.)
The conflicts between romance and duty are likely to be a lot less interesting, when both parties in the romance are supers. When one party in a romance isn't a superhero, then the hero can be torn between her duty to fight evil and her need to spend time with her sweetie. But when both partners are supers, you're more likely to see the kind of conflict between "watching out for your teammates" and "saving your lover." The two lovers will probably have spats over whether they were really backing each other up during that big fight with Dr. Carnivore, or being distracted by their emotions over the previous night's big hot tub misadventure. Or whatever.
Bottom line: Superheroes should mostly date real people, because superheroes are usually at their most interesting when they're spending time in the real world, having interactions that aren't just about punching and being Cosmic. But what do you think?
* Okay, fine. It's more than just a handful of good relationships. People in the comments have brought up a number of good examples, including Apollo/Midnighter, Reed and Sue Richards, Hawkman/Hawkwoman, and a number of others. So there certainly are a decent amount of counter-examples.