Obviously, with the reboot, technically all of Star Trek from 1966-2005 is "Old Trek", but that's 40 years worth of material, and some of it doesn't feel as if it was that long ago. From your perspective, what do you think of as being "Old Trek"? There's no right or wrong answer. These days, I think of TOS, the TOS movies, and TNG as "Old Trek". The last two movies are "New Trek". I think of the series produced after TNG ended as a TV series but before the 2009 reboot as in the middle. The first two seasons of DS9 and the last two seasons of TNG are a gray area where the "Old" overlaps with the "Middle". This wasn't always the way I looked at it, but as most of TNG has moved passed "20 years ago" territory, and after going to the theater and seeing some of these episodes for the first time in a long time, it's shifted my view. Has anyone else's perspective changed recently?
Old Trek: TOS, I love these guys, Kirk, Spock, McCoy, and company, great fun all the time. Rebooted Trek: TNG, and subsequent series. While some was enjoyable, this era never felt as enjoyable as TOS. Latest reboot: JJTrek, back to TOS with Kirk, Spock, McCoy. The fun is back.
TOS is "old Trek", maybe up to The Voyage Home. TNG through Enterprise would be kinda like the "second age" of Trek, in many ways the golden age of the franchise, during which it had the highest profile, in my opinion. It is the third age of Trek. The year is 2013. The name of the place is Bab... oh, wait.
"Old Trek" is TOS. And old because it came out in my little kid days. And I'm old, so TOS is old. TNG onward... I can remember watching that stuff like it was last Tuesday, so in my life it's not old to me.
A decade ago, there was classic Trek (TOS and its movies) and modern Trek (TNG and beyond). Nowadays, TNG is as old as TOS was when TNG was on the air, and relatively speaking, it's getting closer and closer to TOS in hindsight....
Yeah, but TOS is oldest simply by virtue of the fact that it is also first. As far as what I regard as "Old Trek", I'd also have to say TOS is old. This because it was the ONLY Star Trek show made before my time (I was born a little over a year after TOS ended production, but was there for everything else.). That said, for me, there is no "Old Trek", only "Old Randy".
Get off the lawn, young'un! Star Trek was the first ST made after my time. My age was a single digit when it premiered.
Children! I was already into double digits when TOS premiered. But I never watched until TNG came around, so... TOS is sort of Old Trek. Abrams is New Trek. Everything else is just Trek.
Old trek was the Trek movies made before TNG. TOS is ancient- made before Neil and Buzz walked on the moon
Belz makes a good point above about STIV being a kind of dividing line. STV and STVI kind of carry a broader "new broom" feel. Both were made while TNG was in production (the first when it was still the baby of the franchise, the second after TNG had firmly established itself as The Star Trek of the 1990s). It's interesting to note that while STV only takes baby steps towards incorporating elements established on TNG, primarily in terms of showing co-operation between Klingons and Kirk's crew, TUC basically hangs its plot on references to 24th century Trek. In a lot of ways STVI is the most displaced TOS movie, because it's the only one where the goal-posts had moved and nearly everybody involved in it's production kind of acknowledged that TOS wasn't the only game in town anymore. If I were going to segregate my Trek, 1966-1986 would be one epoch, 1987-2001 would be a second epoch. After that Trek turns inwards on itself, becoming much more introspective. Enterprise and NuTrek are both attempts to effectively refresh the franchise by looking backwards instead of forward. They're a distinctly different beast than even the TNG/DS9/VOY era.
Strictly speaking, from my own perspective of what I think is old, it's affected by my perception of previous times. I think the early-'90s are retro. I don't think of the late-'90s as being retro at all. The mid-'90s are turning retro but they're not completely there yet. That and 1994 is a common dividing point when talking about '90s Star Trek. My perspective, as I said, has shifted but it will eventually shift again. Having said that... Looking at another angle, one that's not "what's nostalgic to me and what isn't", I can agree with what Lance said. ST V and VI are a transitional gray area because those are TOS movies that were made while TNG was in production. I personally think late-TNG/early-DS9 are also a transitional gray area where Star Trek was changing in general. It was post-Roddenberry, the franchise was expanding, and episodes like "Chain of Command" and "Preemptive Strike" (as well as the Maquis storyline in general) were different from what we would've seen before. ENT is another gray area. It was developed by the Old Guard, but it was an attempt to get back to characters who were similar to those on TOS: The pioneering Captain. A Vulcan First Officer. The friend of the Captain who embraced emotion, was Southern, and frequently argued with the Vulcan XO. The unexplored frontier. It wanted to get back to TOS. It also wanted to become more contemporary. Aiming for a little more sexuality. It took a look at 9/11, like STID. Taking place before the 2233 split, it's also the only series that survived the reboot. It can be argued that if ENT isn't New Trek then it could at least be Proto-New Trek.
Pretty much this, but I can't quite fit TAS or Enterprise in with oldTrek. They're both so out of place that I consider them to exist in a sort of limbo.
Since the only thing that survived the JJA reboot was Enterprise, here is how I see it: Old Trek: TOS,TAS, TNG,DS9,VOY and movies 1-10, and I suppose technically Star Trek Online if you want to count that. New Trek: Star Trek Enterprise, Movies 11+
Old Trek: TOS, TAS, movies I-VI Berman Trek: TNG, DS9, VOY, ENT New Trek: Star Trek, Star Trek Into Darkness