Depends on what you mean by 'good'. There are some that help the amp sound awesome but don't last. There are some that last a long time but don't help the amp produce the most stellar tone. IME JJs are generally fine and certain types sound really good. I've read others complain about their failure rate, but I personally haven't experienced failures with JJs yet.
All tubes come from 3 factories, 1 in the Slovakia, 1 in Russia, 1 in China. JJs are THE brand of the tubes from the Slovakia. The Russian and Chinese tubes all get rebranded to all the others; e.g. EHX, Sovtek, Svetlana (current production), Groove Tubes, Ruby, Mullard, TungSol, ValveArt, TAD, etc. are all rebrands of either the Russian or Chinese tubes. How good a brand is largely is a factor of how much testing and rejecting of tubes that are outside of desired specs/tolerance. My understanding is TAD does the most testing and is the most stringent in rejecting tubes outside of spec tolerance.
For me, the best current production V1 12AX7 I've tried is a TAD STR. It sounds just like my original Mullard 10M from the 60's/70's. Others that I liked are a Groove Tubes 12AX7 and Ruby 12AX7-C, and a Vokshod 12AX7A. The JJ ECC83S is also good sounding IME. For EL34s, JJ KT77s sounded the closest to the original Marshall-branded Tesla EL34Ms that were in my Marshall SL-X when I bought it. Haven't found an actual EL34 current production model that sounds like an original Mullard or Tesla EL34 yet.