Could some kind soul recommend a good (or at least worth watching) sci-fi movie/series (anime is fine too) that just doesn't get the recognition it deserves... so, no Alien, Star Trek, Gundam or anything else that everyone and their grandma has seen.

Now, I do realize that somthing like "good" is dependant on your personal tastes. The important bit is "lesser known" and "doesn't get the recognition it deserves". 😀

~4400 manga completed
~1700 ongoing...

Crest of the Stars and it's three Banner of the Stars sequels come to mind.
Infinite Ryvius is decent.
Outlaw Star is fun.
Nadesico could probably be called less known these days.
Gunbuster and Diebuster.

As for live-action stuff, well everything I can think of immediately is pretty well known. 😀

Ok, I decided to edit my post and make two categories. "Well known, but have to mention them anyway" and "I have no idea how I found this/new series"

Well Known But Have To Mention Them Anyway:
Doctor Who
"Serenity"/"Fire Fly"
Galaxy Quest
Heroes
Hitchhikers Guide to the Galaxy (I suggest you read the books before the movie-the movie is more confusing without doing so)
Primeval (BBC)
Eureka
Stargate (The show not the movie) and Stargate Atlantis
Person of Interest
Faith (K-Drama and romancey)
The 4400
Sliders

I Have No Idea How I found This / New Series:
The Irresponsible Captain Tylor
The Neighbors
Star Cops
Survivors (BBC)
Jericho
Continuum
Alphas

I'll post more if I can think of them

If you have to raise your voice to improve your argument, it merely shows how weak the ground you stand on is.