How can we break apart each series?
My quick subjective breakdown:
TOS
S1-2 establishment
S3 wavering
TNG
S1-2 trying to catch lightning in a bottle again,
S3-5 core renaissance,
S6-7 running down
DS9
S1-2 tng-lite identity seeking,
S3-6 core melodrama,
S7 endgame mega-arc
VOY
S1-3 more cerebral,
S4-7 more visceral
ENT
S1-2 episodic meandering,
S3 mega-arc,
S4 mini-arcs
EDIT:
TMP Trek meets 2001
TWoK-TVH golden era
TFF-TUC wind down
GEN-FC "good" tng
INS-NEM bad tng
ST '09(-ID?) glossy retro reboot