ずるいずりい、うちのほうが上やったのに上やったのに
Taking 「やった」 as 関西弁の「だった」, does this basically mean:
[Not fair! I was above you.. I was above you...]
or does わたしは「X」のほうが上です。 have another meaning?
うちのほうが上やったのに上やったのに
Yes, this やった is the 関西弁 meaning だった. うち is also typical in 関西弁 meaning わたし. It appears to be saying "That's not fair. I was the one above (someone)." And repeating the last part showing the feeling of resentment.
does わたしは「X」のほうが上です。 have another meaning?Here in your example sentence it's わたしのほうが （Xより）上です. 「わたしはXのほうが上です」 doesn't make much sense. – Chocolate♦ Jul 8 '17 at 5:13