I like feminine/twink guys, so everyone recommending bug buff guys 💀💀

But I'm a gay guy so not the target of OP's question 😅 I just barged in because it's a dry desert in terms of my preferences out there 💀

To sexualize men for women, you have to understand women.

To men, attraction is largely visual. So to sexualize a woman for a male audience means making her look attractive, and dressed in a revealing outfit. Swapping the genders doesn't work. A visually attractive man in a revealing outfit is far more likely to appeal to either gay men sexually, or men generally as a power fantasy. To appeal to women you need a fundimentially different strategy altogether.

Consider erotic literature. Its a genre that is disproportionately popular with women. Its basically anti-porn, no visuals all story. Male characters in these stories are almost always sexualized by women for women. The attraction mostly from their choices and actions than appearance. You need a completely different approach.

Go read some smut. Talk to straight women about who and what they find attractive. You have to learn a lot about women to appeal to them. What they are looking for, and how they are looking for it is entirely different from men.

Watch some episodes of Charmed and look at the characters the sisters are flirting with, they are all different kinds of straight woman wish fulfillment.

Ofc women also sometimes are in the mood to get railed and knocked up, then a big hairy muscular guy is often the thing. But that mood comes upon most women relatively rarely. It's a kind of comfort and trust that makes you want to melt into a guy.

Jiggle Physics Ding Dongs

But how to sexualize male characters and do "fan service" for the female audience?

Easy, just add Caius Cosades to your game:

I think Hades is an excellent example of a game which just sexualizes everyone.

I think you need to check out the genre of Otome games. There's hundreds of weird dating sim style games catered to women which feature a male cast.

It's debatable of how sexualized these characters are. But whatever they do appeals to their female audience.

Werewolf him

Same way. Hot bods, tight clothes, show plenty of skin.

Seconding the otome comment, and a link to a relevant tag on vndb - you can probably find anything from not very sexualized to pure smut on that list, and there's often screenshots. https://vndb.org/g542

Watch jojo. You are gonna get your answer best way possible

According to my wife...

Dress shirt with sleeves rolled up to the elbow.

Kilts.

It depends on the genre of the game.

Fighting games like Mortal Kombat? Put the men in skimpy outfits that show their muscles like the women.

Survival game? I don't need to see the characters sexualized while they're trying to survive a zombie apocalypse. Give me character depth and growth, empathy, and strong story-telling visuals. I'll fall in love with man or woman that way.

Rolled up sleeves. Just trust me.

If it’s uncomfortable and disempowering for men, you’re probably doing it right. It’s often a power dynamic.

But to draw back from a sour take: This will also turn off some people. Both ways. For instance: I love sexualized designs, but some games genuinely went too far. Xenoblade Chronicles 2 and Nier Automata had genuine, serious stories to tell, but fell flat on some people for sexualizing their main (female) characters in such an objectifying way.

I also think for women, the pure visual isn’t quite as important as their movements and actions. That part gets tricky since tastes vary.

There’s a few gacha games out there designed for women that can give an idea of an extreme end to take it to. Again, keep in mind, there’s not one universal appeal for a whole gender (same for guys) so it will often turn out that the most universally appealing designs are the relatively safe ones you already see.