Although I cant off the top of my head without a ton of research demonstrate the original Enterprise was a/the Flagship, I'm almost certain that it was stated to be at some point.
Except that it wasn't.
True enough, Kirk had his ship taken over by flag officers a couple of times, thus theoretically making her a flagship. He himself twice commandeered the ship while holding flag rank, once legally, the other time illegally. But no "special status" was ever established for the ship, save for her holding some speed records as of ST3:TSfS.
the Defiant has some really strong linage as do ships like the Intrepid, the Excelsior, Voyager (now).
Huh? TOS had one starship Defiant
, of no particular significance, and with an ignominious ending to boot. TOS movies had one Excelsior
, a big ship that had all her glory stolen from her by the smaller Enterprise
, twice. There was no Voyager
before Janeway's hero ship. So what's all this talk about lineages?
In the real world, lineages like this don't really exist. In the USN, a "famous" name like Independence
has moved from a small sloop to a ship of the line to an insignificant troop transport, then back up to a light cruiser that was finished as a light aircraft carrier, then to a bigger carrier, but currently is assigned to a modest littoral warfare vessel. HMS Enterprise
is a roller coaster ride from obscurity to prominence and back, several times over.
Does Starfleet assign a given name to progressively bigger and better ships? The Enterprise
is the one known case, but e.g. the Intrepid
would appear to be a contrary case - from the largish and apparently somewhat significant ENT ship to the comparable TOS Constitution
to mighty Excelsior
but then to the class ship of a smallish type.