Jacen said:

And yes, the crawl does suggest that Luke is the leader. I think it was hyperbolic thinking, shocking as it might be that GL would allow himself to be self-contradictory! It's been suggested that GL and only GL wrote all of the crawls for all of the movies.

Well he IS a leader technically. Commander is pretty high rank (the only ranks above that for ground troops are Colonel and General). Even if he does not lead the rebellion or even Echo Base he is a hero for them (shot proton torpedoes in the DS exhaust port without a targetting computer) and a strong symbol of hope ("yay the Jedi are NOT totally gone!")

The rebels don't all take orders from him, but they certainly do look up to him.