Gilbert Melendez is the #2 LW in the world.. possibley the #1 after Edger failed to avenge his loss to the number 3 or 4 in the world.
He has the right to make this claim.
Melendez has not beaten enough quality guys to state his claim as #1, #2 or maybe even #3. Compare the last four wins to Edgar, Maynard and Florian.
Melendez - Aoki, Thompson, Ishida, Damm
Edgar - Penn(x2), Veach, Sherk
Maynard - Florian, Nate Diaz, Huerta, Miller
Florian - Gomi, Guida, Stevenson, Huerta.
Can you see the gap? Not to disrespect Thompson, Ishida and Damm but, they aren't on the same level as Penn, Florian and Gomi.
The way he beat Aoki was impressive but, beating one 'top' guy isn't enough to cement yourself at the top. An example, Edgar wasn't considered to be better than BJ until he beat him the second time.