I think Star Wars and Dune fit the Space Fantasy genre, perhaps Farscape...
I really think a sci-fi genre gets more fantasy the more it waves away the constraints of current science and just "rolls with it." Gravity on ships and stations? Yep. Inertial dampening and FTL travel? Yep. How does it all work? Nope.
We don't care. It just does. The setting is a backdrop for amazing adventures are thrilling tales! So, you can approach your adventures from many angles. What do you want your adventures to be about? What stories will you and your players tell?
Really I love space fantasy because I don't have to explain all the science stuff. It could be recovered lost alien technology, or some strange extra-dimensional power source, or an altered state of mind. Doesn't matter. Just put stuff in that's COOL. Turn the dial up to 11 and toss in stuff that you think will make the game fun.
True 20 is an excellent choice for this. There is enough options in Revised and the Role source books to play without much (if any) need for tweaking. Have you checked out the
Lux Aeternum setting? Great setting and ready to roll with True20. Has a nifty swashbuckling space fantasy thing going on with a mix of old world and new world tossed together. Worth checking out!
Also, I love Malhovoc Press stuff. Monte Cook is a genius. I think the
Chaositech supplement is great inspiration for a dark themed space fantasy. This book creeps me out, and that is awesome.

Something else to toss in there.
For another game line that touches on both these (and well I might add) subjects check out
Starblazer Adventures and
Legends of Anglerre for the FATE system. Even if you don't use the system, the ideas and advice are very universal.
Also, you can toss in the
Cthulu mythos and
Cyberpunk ideas with two really well done True 20 supplements.