The US debut wasn't until two days later on September 8, as you'll see referenced around the Internet. But thanks to Wikipedia and the Google News archives, you can see the historical record of the earlier Canadian debut via the Montreal Gazette (page 37). Look at that, actual printed material used to let people know what's on television...old times indeed.
I grew up in the 1980s, so I never saw any of the original series during that first run. I remember seeing a lot of the re-runs, though, and more importantly the movies. The Wrath of Khan/Search for Spock/Voyage Home movie arc was what really made me a Star Trek fan. The newer movies aren't nearly as good, but I've still watched them all, and mostly enjoyed the experience.
As far as the various series go, I've watched them all and have no complaints. Some are better than others for sure, but even the weakest (yes, Voyager, I'm looking at you) have plenty of good moments. The Next Generation is still my favorite, probably since it was airing during my high school years. Perfect time for forming obsessions! That series turns 29 this year.
Coming up next year will be a new series, called Star Trek: Discovery. I'll probably watch it at some point, though not right away since it's only going to be available on CBS All Access, which I have no desire to pay for. Eventually it'll either be available on some other service that I have access to, or once a season or two is complete I can pay CBS for a month while I watch the whole thing.
There's plenty going on this year to celebrate the 50th anniversary of the original series debut. The postal service has printed up stamps. There was a big convention in New York. There's a bunch of stuff on sale in the official store. Roddenberry Entertainment is publishing some of Gene Roddenberry's original notes online. Marketplace Tech is gathering stories from people about their favorite Trek episodes, for use on their NPR radio broadcasts. No lack of effort in marking the 50th anniversary.
Happy birthday to the Star Trek universe!