if each series was a motor vehicle:
TOS: 1967 Corvette Stingray. It is awesome. It's value will only increase in time. It has design flaws, idiosyncrasies, and if you expect too much out of it, it will wrap you around a phone pole killing you and destroy itself. But that's okay, because it is that freaking awesome.
TAS: The Matchbox car of the Corvette Stingray your brother gave you because he was grown up and into girls now. It's still kind of cool. Not exactly the same. But you can pretend.
TNG: 1987 Honda Accord. No matter what happened it always got running. It may have had a few recalls at the beginning, but it never failed to get the job done, and it never broke down. Briefly out of style, it's now old enough to be retro cool again with ahem, and another generation ready to appreciate it.
DS9: Used Winnebago. Rarely does it go anywhere, but it's what happens inside that counts. There's a lot of chemistry and drama going on inside that home away from home. It isn't going across country to discover new things very often. It might even get dark in there, but there will be a laugh or two along the way. And violence. But you can handle it. You CAN handle it. No one will get why you like it.
VOY: 1998 Buick Park Avenue Ultra. Your aunt bought it and thinks it's cool. You better not tell her otherwise. You can't help noticing the air freshener pine tree hanging off the mirror is the same one that was the old Accord before you sold it. Not one like it.. the same damned air freshener. And it's not very fresh in there. You could build it into a hot rod but your aunt won't let you.
ENT: Pontiac Fiero GT. People were really excited until they saw how it looked. A few were still curious until they saw how it performed. Then hardly anyone wanted it. Three years later they upgraded it to a V6 and it all the flaws were fixed, but no one noticed and it sat at the dealers till it rusted. Sometimes found near the DS9 Winnebago.
DSC: Yamaha V-Max. What board room chaos led to a severely overpowered motor in an almost criminally underbuilt chassis? It reaches beyond its grasp. It punches above its weight. If it does anything beyond a straight line, it will probably kill you. The brakes are purely theoretical.
PIC: Cadillac Hearse. It has all the finest appointments. The attention to detail is all there. Power is smooth and confident, even if it never goes fast. People slow down to watch as you pass by in it. It seems to have a universal appeal that you can't quite put your finger on. Maybe if you could get out you could see it objectively from the outside, but for some reason you can't leave.
LD: Vespa GTS 300. No one takes it seriously. That's fine. It gets you around. It has room for everything, and if you look under the seat you might even find your old TAS matchbox car. But the quaint polite smiles drop when it disrespectfully blasts by a certain hearse at 90mph.