Now, I always imagined that Dr. Manhattan seemed to start out as still being heterosexual and interested in sex/relationships, but gradually over time, as he became more removed from humanity and more absorbed in the science of the universe, he became removed from sex too. He says something like wanting to please Laurie and not knowing what stimulated her anymore, as well as having split into three or so bodies with one of them still focused on working, showing that his interest between Laurie and science is divided, with science being the dominant one.
Which does make me think how, after the accident, when Jon Osterman becomes Dr. Manhattan, once Janey Slater grows old, he basically loses attraction to her and moves on to the younger Laurie (anyone find it a bit weird that she's 16 while he's...well, much older? Or the fact that Laurie would find someone like that attractive in the first place?). I wonder whether or not he would've left Janey due to her becoming old even if he wasn't Dr. Manhattan, or that his new body rendered him unable to hold attention to things for long periods of time, which only got worse coupled with his growing detachment from humanity (supported by the scene in Vietnam with Dr. Manhattan taking no action in the Comedian and the pregnant Vietnamese woman's altercation).
Maybe so. He gets bored with Janey; jumps to Laurie. Nuclear war's about to break out; pressure to perform is growing stronger (no crimefighting left to keep Laurie entertained, and despite apparently feeling obligated to don the revealing costume and crimefighting to please her mother, who wanted to live through her and regain the years she'd lost having a child, maybe she herself had a strong focus on sex that Dr. Manhattan couldn't fulfil). Goes to Mars and builds some...metal building thing. Presumably gets bored with that and goes back to Earth in order for Laurie to persuade him to save Earth. Discovers "thermodynamic miracle" (possibly an excuse for Manhattan to return to Earth; maybe he really does still partly care for Earth, or it's just another time-killer for a man who time is simultaneous for) and decides to saves Earth. Returns to Mars or some other place in the universe to create new life, akin to a god. All the while growing in knowledge and exploring new facts/theories about his science and stuff.
This is also probably parallel to at least one perception of the Judeo-Christian god, but also the Greek gods (going with his design): something about having the ability to do good, but refuses to for the sake of a "test" or just because he doesn't care, perhaps being nihilistic. Also, during his reconstruction, he did away with his hair and pupils, yet retained his penis. Perhaps this was out of some subconscious sexual desire that still remained within him to regain his manhood or cling onto what would be a focal point in his relationship with Janey and, later, Laurie. I wonder if, after breaking up with Laurie, he'd just do away with his penis, if he had the ability to. I always wondered how it'd be for both him and his partner to have sex because, as Sally told Laurie, she was almost literally having sex with an A-bomb. With Janey, I guess it was still love for Jon. With Laurie...perhaps she was fucked-up because of her upbringing by her highly questionable mother (who encourages her daughter to dress up in a costume arguably even more revealing than her own and take up crimefighting at the tender age of 16? I'm almost tempted to call repressed lesbian/incestuous tendencies, but even that might be looking into it too deeply).
All this has made me think that this Before Watchmen series, despite not being written by Alan Moore, might actually be good if it handles the backstories of such characters as the Comedian and Silk Spectre with delicate finesse. The only "normal" main characters (or, to be more accurate, the only superheroes without any social problems) in the graphic novel seem to be Daniel Dreiberg and Hollis Mason, incidentally both having taken the mantle of "Nite Owl" (a.k.a. Batman; another contrast that's probably already been brought up, as well as neither Dreiberg nor Mason being as dark/non-nerdy/probably rich/in mental turmoil as him). I would include Laurie Juspeczyk if not for her attraction to Dr. Manhattan. If you think Dreiberg's apparent impotency outside of his costume makes him "abnormal" or socially awkward because of this, then I guess Mason is the only "normal" superhero in Watchmen. And yet, in probably one of the most unfortunate and saddening moments of the book, he's killed in cold blood due to a catastrophic misunderstanding inadvertently brought about his successor.