Sopranos had a good ending, which fit Sopranos's style.
BB had a good ending, which fit BB's style.
If you have an ambiguous, more interpretive ending like Sopranos, you get blasted by critics for not having a pay-off or toying with audience expectations.
If you have a more definitive, climatic ending like BB, you get blasted by critics for "pandering to the audience" and tying things up in a too-pat way.
You literally can't win no matter what you do.
Sure, there are endings that stink like Dexter's, but that's a quality issue. There's different styles you can approach an ending with and Sopranos and BB just chose differently.
I agree. There is no objectively superior way to end a show; the narrative itself informs the perfect ending. I haven't seen
The Sopranos yet (don't worry, the ending was spoiled for my long ago), so I'll go with another example of a perfect ending:
Angel's "Not Fade Away." The overarching theme of the entire show was that redemption is not an endpoint, it's a constant struggle, complete with setbacks, failures, recoveries, etc. So the show ending with Angel and co. charging into the breach once again, regardless of the friends they'd lost and the horrors they'd been through, reinforced that message that their fight never ends.
For
Breaking Bad, which was very much the story of Walter White's rise and fall (or fall and rise, depending on your perspective), it had to--
had to--end when that scenario ended, which was appropriately (given all the crap he'd done) with Walt's death. There was no redemption for him beyond finally taking responsibility and closing the circle, effectively recognizing the blight he'd unleashed on his little corner of the world and ending it. Would I have liked to see Gretchen and Elliott bicker over the money until they ended up in a messy, months-long divorce? Sure. Would I have liked to see Jesse visit Brock at whatever orphanage or foster home he ended up in one last time before riding off into the sunset? Absolutely. But those things are all secondary concerns, out of the purview of Walt's--and, by extension, our--concerns. The ending was perfect.