Let's see, everyone knows Natsu's strength is superior to Gajeel for not too much, and natsu in the end had to recieve help from Laxus in order to beat Gajeel, it's safe to assume that out of 10 fights between Gajeel & Gray, gajeel will win 9, he will lose one due to tripping over a rock and hitting his head. (jk on the latter) xD