Can only Jedi see Force ghosts?

I've looked high and low on this board to find an answer to this question but I can't find it anywhere.

I finished RotJ again the other day and began wondering. At the ending Luke sees Anakin, Yoda, and Ben, but it appears that he's the only one that sees them. With all the other people there, Ewoks, his friends and other rebels, you'd think that at least a few of them would see them, especially Leia, as she comes over to get Luke.

For some reason I'd never thought about this before and now it's bugging me.

 

I think so. Ive read a theory about Force ghosts that a dead person can attain identity once learned it while one with the Force. Another thing is you must have a strong connection with still living beings. Like Qui-Gon, he has somewhat attain his identity inside the Force because he's strongly connected to Anakin, but he hasn't learned it, and it was Yoda who perceived him. Those who are still living and want to become one with the Force immediately but also want their identities remain, he must be at peace. We can see Obi-Wan meditating in ANH before vanishing, and Yoda seems to be at peace. That vanishing is the process done by the Force for the living who want their identities remain. Maenwhile, Vader tried to learn it upon seeing it done by his former master (wonder why he is inside his meditation chamber in TESB?). Those that are not physically strong in the Force can master it once he died, like Kyle's Father in Jedi Outcast, but I think it's EU stuff.