To be honest, I gave up on The X-Files after the pilot, and only gave it a second chance after it became a worldwide phenomenon. And, as I recall, the pilot for B5 struck me as one endless expository lump.
But you're forgetting the very best line in the FS premiere: the bit where Crichton steals an alien blaster and threatens to fill with the bad guys with "er, little glowy balls of light!"
Which was not only a funny bit, but also conveyed the show's breezy, irreverent tone, while getting across the fact that Crichton was very definitely a fish out of water!
By contrast, the B5 pilot struck me as much clunkier and more ponderous--or so I recall. I admit I haven't seen it since it first aired.
Then again, even TNG didn't really get good until Season Two . . . .