Depends entirely on your parents and how they show (or not) favoritism and to whom.
In my family, the oldest is the golden child. My mum claims this (she was oldest), she treats my older sister a whole load better than me, I heard her tell my older niece that the firstborn is always special etc etc.
Older sis, compared to me: bigger bedroom, new toys, held up as a paragon I should copy, her choices count for more because she's older (I'm 48, this still happens), got stockings etc until she went to college, but they stopped when she left even though I was still at home, always gets first turn, first choice etc, her children are more important than mine etc etc.
So - really it has nothing to do with being the oldest, and everything to do with my mum's favoritism (which stems from her younger brother usurping her because boys are better, I'm sure).
DSis also gets LOADS more time/money support from parents, although she doesn't work and is married to a multi-millionaire. I work FT and we get very little in comparison.