I think it's safe to say that it's hard to love a Winchester boy. Not that it's actually difficult to fall for one of them, but that the likelihood of that relationship working out long term is next to zip. Not only would most sane girls not be willing to give up a normal life to ride around the country fighting really scary dudes, but I'm pretty sure some of the fans would do her in.
Supernatural is, above all, about the relationship of these two brothers. Other characters can be secondary at best and more commonly window dressing or "victim of the week." This is why there is fan outcry when things happen like the introduction of Ruby and Bela or the upcoming episode in which we will evidently be introduced to a third Winchester brother. Some fans don't want to shift the focus off Sam and Dean, and I suspect some don't want any girlfriend material in there so they can continue imagining themselves in that role. :)
Let's face it -- if you're a girl and you get introduced on Supernatural, my bet is that you're not long for this world or that we'll soon be seeing you in the Impala's rear view mirror. This trend is set early when Sam's serious girlfriend, Jessica, is killed (like his mother was) in the pilot, as soon as he heads back toward the supernatural-hunting life. The girl who we learn in "Route 666" was Dean's foray into a serious relationship, Cassie, is a casualty (though she's still alive) of the boys' hunting lifestyle too. One of the saddest, tear-inducing episodes for me has been "Heart", in which Sam finally lets go of Jessica enough to fall for someone else. Too bad Madison ends up being a werewolf and he has to kill her.
I'm sensing a trend here.
But here's the thing -- the boys have given so much, worked so hard, been to hell and back (Dean, literally) that I think they deserve to find love and somehow live a happily ever after. Somehow I don't suspect that's in the cards. I'm not sure they'll even survive in the end. And if they do, how do they leave all they've seen and done behind to marry and raise kids in small-town America or suburbia? Do you think that's even possible? Will there ever be no evil baddies to fight?
If the writers somehow make this possible, what kind of women do you think they'll have to create as potential love interests for Sam and Dean to make the fans happy? How soon before the series finale do you think these women can be introduced so that the fans don't revolt? Or do you think we've already met them. Have to say that Anna grew on me in the recent episode, "On the Head of a Pin." The only way I can see this is if somehow God or the angels can wipe their memories of all the bad stuff and allow them to start with a fresh slate. Could that be their reward for helping heaven defeat Lucifer and his minions?
I'm curious what you think. Is long-term love in the cards for the boys?