I think we need to divide rape up the way we divide murder up - but in four degrees, not three. First degree rape would be where the victim and the rapist are fully aware of what's happening, and the victim is clearly opposed to the idea but can do nothing to stop it (prototypical rape in Grand Central Park at midnight sort of thing; also, rape of minors by their parents or other family members; rape of wives by husbands; etc). Violent rape, basically. Life without parole, medical experiments and forced labor for these f***ers.
Second degree rape would be "I'll fire you if you don't suck me off" situations - i.e. no physical, violent coercion, but a clear threat nevertheless. This includes threats of violence to others, demanding sex as a bribe, offering to exchange sex for a promotion or raise, etc. Abuse of power, essentially. Second degree rape would also cover situations in which a lucid rapist drugs a victim or gets them drunk. I'd say fifteen to twenty years' hard labor.
Third degree rape would cover things such as sex obtained via gratuitous lying (I'll give you money to get through college; I'll hire you as a porn-star if you let me tape us screwing; johns running away from their prostitutes; etc.), in other words, situations where the rapist has no actual authority or power over the victim but purports to confer some concrete, tangible benefit to the victim for sex and then fails to deliver, either out of malice or because there was no possibility of providing that aid in the first place. Ten to fifteen for these ones.
Fourth degree rape would be rape where rapist (and possibly victim) is under the influence of substances or has otherwise medically impaired thought processes (especially if there is reason to believe the rapist's intoxication took place first, or at the same time as the victim's), but where the rapist ought to have known that sex was unwanted. This kind of thing happens unfortunately often in our culture, and intoxication does mitigate some responsibility, so I'd say five to ten years.
Some caveats - first, evidence needs to be very clear. If there are to be character examinations, then have them be of both the plaintiff and the defendant, not just the plaintiff. Yes, women can lie about being raped, but men can also be misogynistic jerks. Second, situations where a woman had sex with a guy and then decides she wished she hadn't aren't rape.
Third, situations where a guy (or girl!) lies about things in general - like claiming he's a doctor, rather than the waiter he really is; or failing to disclose that he has casual sex with someone else regularly - aren't rape. No tangible benefits lied about. We need to be careful, or we'd end up on a slippery slope where it's a rape-defining lie if a woman says her favorite color is green and you agree just to get in her pants.
Fourth, statutory rape laws are often just ridiculous. Where I live, the age limit is 14, which makes way more sense than 18 - though 15 or 16 is acceptable, in a pinch. Come on.