In your order of preference.
1 - Deep Space Nine (most consistent and highest emotional investment for me, loved the tone, the storytelling, and the characters)
2 - The Next Generation (most familiar and comforting for me, it's the most purely watchable)
3 - The Original Series (campy and inconsistent at times, but excellent sci-fi stories)
4 - Enterprise (I'm still working my way through season 3 but so far I think it's a better production than...)
5 - Voyager (still enjoyable but lots of wasted potential and highly formulaic)
Haven't seen TAS, and it's obviously too early to place Discovery.
1 - Deep Space Nine (most consistent and highest emotional investment for me, loved the tone, the storytelling, and the characters)
2 - The Next Generation (most familiar and comforting for me, it's the most purely watchable)
3 - The Original Series (campy and inconsistent at times, but excellent sci-fi stories)
4 - Enterprise (I'm still working my way through season 3 but so far I think it's a better production than...)
5 - Voyager (still enjoyable but lots of wasted potential and highly formulaic)
Haven't seen TAS, and it's obviously too early to place Discovery.