Classic Star Trek. I mean anything from TOS thru Enterprise, depending on how old you can tolerate. You'll want an episode guide to make sure you're not watching a shit-tier ep or part of an arc, but most episodes are going to tell a good solid sci-fi story in one sitting.

Sliders is another good one for speculative sci-fi. The Outer Limits for an actual anthology of stories.

Classic Star Trek. I mean anything from TOS thru Enterprise, depending on how old you can tolerate. After TNG you'll want an episode guide to make sure you're not watching a shit-tier ep or part of an arc, but most episodes are going to tell a good solid sci-fi story in one sitting.

Sliders is another good one for speculative sci-fi. The Outer Limits for an actual anthology of stories.