I think it is hard to teach kids to dream about the future and what they want and keep them anchored in the present at the same time. I did not have any trouble with the mansion/TV/car response and he thinking it is "funny"; I have no trouble with him wanting those things but he needs to learn to also stay in the present (size of pizza slice).

Sounds like he could be a little anxious about where things come from and whether he can/will get what he, himself, wants in the future. It is natural when someone says, "what do you want" to put thought into it! We are the only ones who can get for us what we decide we want.

I would look at my own attitude toward material things and how they remind me of my ex-, etc. and how that could get in the way of helping my son learn about the world. Wouldn't you like a larger house or better car, etc. if you could afford it? An 11 year old does not understand how much these things cost and what relationship they have to pizza (or going to college, another "thing"/education). If he puts big things on his lists, I would laugh with him and say something innocuous like, "wouldn't that be nice if we could afford that!" but I would get down on his grabbing the first/largest piece of pizza. That may not be all greed but worry about getting his "share" of life? If he looks around and knows how hard you work and looks at what his friends/acquaintances might have that is an unavoidable lesson too? I would give him reassurance that he will always get enough pizza but not always the first or biggest slice. I would set clear rules about who dishes out the pizza slices (you) and treat it more like a lesson on manners instead of life? Picking gifts for others, too, if he does not know the friend/relative that well or care that much about them (how does he do picking out for his brother or you?) he may need a little more guidance from you too; make it a game and have him find 3 things he thinks the other person would like and tell you why/try to sell them to you and you'll pick the "best"? That can give you an opportunity to teach about relative worth of items (easy to pick out a house/TV/car but "more expensive than I would like to spend right now" versus "too inexpensive, this person is more important to me/you/us" can get him thinking about choice in what to spend money on, too).

There is nothing inherently wrong with liking big, new things and going after them or inherently right in preferring to make sure other people are served before one serves one's self; they are personal choices. A parent can do a lot of guiding by example and by what choices they give a child but can't ultimately help a child by making it look "bad" that they want a bigger house, TV, car? All that does is add guilt to confusion instead of educating. Grabbing pizza slices is a boundary thing; you are in charge of dinner/your house, who gets what, not your son.

Wanting a big slice of pizza is not bad but he has to learn to ask, "Mom, may I have that big slice of pizza there?" and have you say, "Sure, let me get your bother a slice first and then I will serve you" or, "I would prefer if you had a smaller piece and then a second if you still feel hungry" or something like that. If all else is equal though, if the boys don't fight about who gets what and you don't want to always have to serve the pizza, that he wants/takes the largest slice is just something you would not choose to do? I know I was taught by my mother to serve the "man" the largest piece of meat and I'm 63 now and still have difficulty giving my husband a smaller piece of meat than mine I wish I had been taught "about" things and given choices rather than just given directives (don't grab the biggest slice of pizza). It has been harder to teach myself that I am "okay" and unteach myself the arbitrary rules my stepmother lived her life by? I want to respond to the other people and situations, not to my own interior set of arbitrary rules taught me.