What is the best sounding Mahler symphony cycle?

Re:Budapest. I didn’t say they’re terrible. Just way way overrated. 
Good choices above from both of you. The Mehta LAP Mahler 3 for me is a bit polite. Very well done played but the recording itself strikes me as being from just a bit too far away. It looks like the preferences for both of you skew to older recordings perhaps hints at your generation. My preference skews towards many of the newer recordings from the big 5 plus LA with notable exceptions for Chicago and LA from the mid 20th. 
I have many of these on vinyl as well (not the most recent ones of course which aren’t on vinyl)

It seems both of you like the Bernstein #7. An excellent performer, but I never felt the brass in the NYP from that era up to the task of the very brass-heavy 7. I’d recommend the Cleveland (Boulez - 1996) recording. It’s simply stunning. 

My choices have to do with vinyl being my primary source, but I guess they date me as well 😕

On original vinyl the Mehta #3 has no rivals sonically, although as a performance the Bernstein (both the CBS and DGG recordings) may be superior.

I forgot to mention Das Lied von der Erde, but here Klemperer on HMV Angel has my preference (yep, another oldie). As for #10 (Cooke version), I like the Rattle on EMI, but I'll admit that I haven't heard any other performances.

I mentioned in my first post in this thread that I hadn’t sampled to many of the newer Mahler recordings as was therefore interested in some suggestions.  The Budapest cycle is the relative new comer for me, along with the other Fisher brother.  I have the Boulez/Cleveland Seventh, but haven’t played it in a dogs age.  Maybe time for a spin.  Abbado/Lucerne or Chicago or or MTT are the other Sevenths that I reach for.

Although I can't say who has produced the best cycle because there are so many variables I have to agree with @schubert  that every one of Fischer's efforts with the Budapest Orchestra is superb in sound and playing but there are many individual symphonies that I just couldn't let go. So for me the jury is out but I still love Fischer's efforts.

I very much like Boulez’s Mahler interpretations. I find them more intimate and less grand than my favorite conductors; eg, Bernstein, Abbado. It's a different take on Mahler.
The VPO recordings have the best SQ in the cycle probably due to the sonics of the wonderful Musikveiren and the recording techniques used.
Not quite audiophile, but worth having a listen.