First, the OT is both of our books, and you can't lay exclusive claim to it. And secondly, Christians don't believe one is superior to the other as they are all one writing. It is all tied together completey intertwined and inseparable. It is just the New Covenant supplanted the Old Covenant.
And from a Jewish perspective you could not be more wrong. You can say it all day, all night, and well into next year and you would still be wrong.
And your last sentence makes your second sentence false. If you do not believe one to be superior to the other, then why did you supplant the other?
One entry found. Main Entry: sup·plant Pronunciation: \s?- ' plant\ Function: transitive verb Etymology: Middle English, from Anglo-French supplanter, from Latin supplantare to trip up, cause to stumble, from sub- + planta sole of the foot — more at place Date: 14th century
1: to supersede (another) especially by force or treachery
2 a (1)obsolete:uproot(2): to eradicate and supply a substitute for <efforts to supplant the vernacular> b : to take the place of and serve as a substitute for especially by reason of superior excellence or power
synonyms see replace