What he means:
Pantherlily could've just been another flying cat, man. He could've just been one more Happy or Lector, someone about ankle-deep with a bare minimum of reason to hang around. He could've been this comic relief kinda shit with no real reason to be involved in dangerous and tense situations. Instead, he's a rich character with his own complete story before he even joins the heroes, a relatable person, and a badass warrior who can go toe-to-toe with the likes of Gajeel and Erza to boot. We know that if Pantherlily were to be separated from Gajeel, he'd be just fine on his own. And we also appreciate when he is around Gajeel, because it's a real platonic bond between two characters that aren't drawn together through any sort of romantic attachment for a change. When you see Pantherlily covered in armor and wielding a 30-foot-long sword and held up in the sky by ten-foot wings, you know full-fucking-well that he is not some chump that will get taken out by the Power of Friendship™ and a Nakama Punch, and you also know that he's the perfect partner for Gajeel Redfox. Have I mentioned I want to bury my face in his fuzzy pecs? I'm not a furry. Always love Pantherlily.