No one is getting any preferential treatment. There is only one line for guest workers. Do you understand the difference between "immigrants" and "guest workers". Immigrants come here to spend the rest of their lives here and become citizens. Guest workers just want to work here until they can afford to return home.
They are apples and oranges. You can't say that rules for one group are fair or unfair to the other. No one goes in front of anyone else or gets preferential treatment.
I'm sure that's the way you see it. But, have you ever heard Bush talk about his amnesty program for anyone other than hispanics. Has he ever included Poles, Russians, Asians Iraish, Africans, etc. in his talks? Never.
There may be two lines as you say, but they're line jumping whichever one you choose. Anyway, our illegal immigrant population, from the looks of things, are in "immigrant" mode - since their numbers are constantly increasing. The dream of returning home is precisely that - a dream. They'll probably be buried in Mexico, but that's about it. That may have not been their intention at the start, but it is now their reality. And that's just another reason why shoe-horning them into a guest worker program won't work. A half-dozen or dozen years in the US is not going to put them far enough ahead to where they'll head back to Mexico. We're not seeing that in practice.