Maybe not classic TV, but the best of American TV? Maybe. Probably. Best writing versus best show are of course a different thing (listen to a raging cinephile argument over Kurosawa v. Ozu to show that clearly), but I suspect both those shows have legs.
Breaking's main narrative path is unique in American television, no? All while being popular. There are already shows that seem impossible without it (The Americans?). I place it way, way up on the list as a managed project (something American serial series rarely are). As a whole it's an amazing story and as episodes name a bad one? The Fly? It seems you think it's overrated. Care to explain?
Barring shifting cultural norms where Modern Family would age quickly (say the gay parents and immigrant jokes), signs point it to already bumping others off top slots (watch the 30 Rock and Parks and Rec Emmys plummet once MF showed up). The writers have a pedigree and it's wrestled comedy back from total snark/sarcasm while its jokes come as fast as Seinfeld. I'm less sure on this one, but I think it would be a mistake to write MF off as another Home Improvement, Three's Company, Will & Grace, etc.
Then again if you told me while The Sopranos was still on the air it was already being overthrown, I'd not have believed it.
All the talk of The Wire in the other thread has me thinking about my favorite shows. I try to be cautious about recent/contemporary shows, and to be fair I haven't steadily had a television for years so somewhat blind. That said here's my list (sorry comedies).
1. The Twilight Zone - No one handled the episode format better.
2. The Wire - No one handled the season format better.
3. Breaking Bad - We'll know for sure shortly, but likely no one has handled the series format better.