Your moniker suggests sound quality is of importance, so with that taken in consideration:
no.1: Walter on US Columbia
no.2: Klemperer on UK Columbia (emi)
no.3: Mehta on Decca/London
no.4: Szell on US Columbia or UK Columbia (emi)
no.5: Barbirolli on HMV (emi)
no.6: Barbirolli on HMV (emi)
no.7: Solti on Decca/London
no.8: Solti on Decca/London
no.9: Walter on US Columbia
Lied von der Erde: Klemperer on UK Columbia
I realise that the original issues of some of these recordings are in the collectors category and priced accordingly. In those cases (like the Klemperer no.2) you should try to find an early reissue, which usually will sound pretty good for much less. Enjoy the ride!