1. Someone he can trust — not just with going out dancing with the girls, but with all his secrets and weird, dumb fears. Trust is the foundation upon which all relationships are built, and mutual respect is the mortgage with which you pay for that relationship, or something. My point is: Trust is huge for anybody anywhere in any kind of relationship, and it's no different for guys looking for life partners.
2. Someone who supports him even if he suddenly wants to quit his job to pursue his dream of becoming a famous screenwriter/inventor. Sure, that might sound easy now, but what happens when he loses his job, or decides he really needs to take a huge chunk of savings and start his own company, or pursue his dream job at 40? It takes a lot of patience, love, and understanding to support your partner when times are rough and there's no sign of when it'll get better. And that's a two-way street, because guys also want...
3. Someone who has drive and ambition, and doesn't just sit around posting motivational quotes on Facebook. Personal happiness is key to a healthy relationship. You should have goals as a couple, and also individual goals, and the way you make it work is figuring out how to juggle all of that at once.
4. Someone who wants to spend time with him, but also goes out a few times a month on their own. I don't think anyone has ever described their perfect mate as "someone who would, if it were possible, literally graft their skin to my skin so we could never be apart." Someone who has their own life and hobbies and passions is always a good thing.
5. Someone he can have really (really, Really, REALLY) great sex with. Sex isn't the most important thing in the world, but it's up there. To be clear, that doesn't mean every guy is out their looking for their own personal sex goddess, just someone they're compatible with; whether that's some vanilla sex once a week or someone they can get kinky with thrice a day.
6. Someone who accepts that maybe he's not the best communicator and understands that he's working on it. Yeah, people need to get better, but human beings are dumb, weird, stubborn idiots, and it's important we recognize and accept that in each other. Be forgiving of the little things.
7. Someone who shares his values and ideals, and knows that no matter how much they argue, it will never be about anything serious. It's important when you get married, but it's even more important when you have kids. Otherwise, they will sense the weak links and destroy you.
8. Someone who keeps surprising him because they're always changing (but not into a werewolf or something, just growing as a person and taking on new challenges). You know those people who seem really interesting at first, and then you realize they have the same three stories that they tell over and over, and that's really all they got? Yeah, the opposite of that. But still, not a werewolf.
9. Someone who speaks their mind. Communication is paramount, so being able to voice what you want, what's going well, and what isn't is incredibly important to a healthy relationship. I guess, alternatively, you could also not care about anything and not contribute to your relationship. That could work too, maybe.
10. Someone who wants to learn about him and grow with him. You know, someone with whom he can live a long and rewarding life. NBD.