Ross knows a lot about dinosaurs and rocks, which is great, but it doesn't give him the right to believe he's better than everybody. However, in the Wonderful World of Ross Geller, being academic instantly transforms you into someone who's better than anybody who isn't. And he's not afraid to show his disdain for others: he constantly mocks Joey, who may be less intelligent, but who also has much more success with women (something that Ross detests). But, above all, it's incredible how condescending Ross can be to his girlfriend (and supposed "love of his life"), Rachel.
Ross even makes a list of what he dislikes about Rachel, which includes things like "spoiled, too into her looks, is just a waitress". Ok, Rachel can act a little spoiled, but she abandons her whole life and starts working as a waitress so she doesn't have to go back to living with her parents (or a husband she doesn't love). Isn't that worth keeping in mind? Sure, Rachel worries about her looks, but that's precisely what leads her to a job in the fashion world. And, finally, "is just a waitress"? So Ross is a classist AND a prick.