I love it, too; I started watching TOS in September, 1966, on NBC and loved it. TOS is my sentimental favorite, with VOY my modern favorite. I like all the episodes and don't have any complaints.
My favorite is "Muse," with "Blink of an Eye" a close second. I like the classical/historical aspects of those two -- and with the latter, the fact it spans all the time frames and comes into their space-faring present. It doesn't hurt that Daniel Dae Kim as Gotana-Retz became a TV star I could see elsewhere.