Barbie all the way for my little miss 4 1/2! But we also got her some dress ups, a craft box (with glitter, stickers, coloured paper, scissors ect...), story books about things she loves or what is happening in her life (we got a book about going to pre school, one about dancing and a barbie story), some activity books with NSW cursive writing in it (sheis learning to write and LOVES to write at the moment), some playdough and playdough tools (roller, cutters, ect...).
Big thing we got for all of them is a swing set.

How about some outdoorsy stuff, like a soccer goal thingy, or those tennis sets with the ball on a string, a mini tramp, sand pit, water play table, slip n slide, subby house. OR some kitchen-ish stuff, like pots and pans, maybe a kitchen if she doesn't have one? Even if she doesn't kitchen stuff with playdough goes down well at our house! My DD loves it!! Or a dolls house with little dolls/people. Educational stuff like leapfrog or vtech computer-ish things.

HTH, and Good luck!