Mostly a fan of the Original series and the animated Trek. Watched TNG when it was on but it's aged badly for me. Never saw more than an episode or two of the other series, not interested.

I guess I like the giant outerspace menace epsiodes. The stuff that feels like an old sci-fi comicbook.

Favorite stuff:

The Galileo Seven - Love this episode! It drops you right in the action and everything feels so bleak for the lost crew. Spock is at his jerky brilliant best.
Spectre of the Gun - The minimal sets of Trek's alien planets never felt more obvious and inspired than here. The red sky feels utterly apocalyptic.
Doomsday Machine - Giant outerspace menace.
The Devil in the Dark - The monster scares me. Great horror atmosphere!
The Immunity Syndrome - Giant outerspace menace.

Someone earlier mentioned BREAD AND CIRCUSES, good call.

The stuff I don't like:
Miri - B00000oooo.
Charlie X - Hissssssss.
And the Children Shall Lead (see a pattern here?) I'll take a goofy episode like SPOCK'S BRAIN over this stuff.

Animated Trek at it's best felt like a more fanatstical season three episode. Goofier and more overtly sci-fi. The two alien crew members added to the bridge are nothing more than cyphers and add nothing to the show. But utilizing the same writers, actors, music and f/x go a long way in selling it to me as real Trek.

Favorite Animated:
Yesteryear - Great episode about Spock growing up on Vulcan.
The Slaver Weapon - A Kirkless crew battles psychic cats for an ancient weapon of ultimate power. It's even better than it sounds.
One of Our Planets is Missing - Giant outerspace menace.