No he isn't, not until he steps up into the UFC and proves it. It's all well and good beating the likes of Thomson, Ishida and Aoki, but until he steps up and beats the likes of Edgar, Maynard, Sotiropoulos, Miller, Penn, Florian, Pettis etc he isn't the number 2 in the world. He's top 10, but until he steps up and joins the elite 155lb division in the world I refuse to rank him Top 2. I rate Melendez very highly, he has a very impressive skill-set, the way he shut Aoki down was very good to watch, but he simply doesn't have the resumé to be ranked Top 3 yet for me.
So, first, BJ doesn't even fight at 155 anymore, that needs to be made clear first and foremost.
Second, what has Sotiropoulos, Pettis, Miller, or Florian done to be ranked number 3? Beat Joe Stevenson? Beat Ben Henderson? Beat Mark Bocek? That is all it takes to be number 3 in the world? Hardly. Unless you think Alvarez is number 3 and Melendez is 4 you have serious problems.
Being a UFC employee doesn't make you better than everyone. Three of Strikeforce's Champions could very well be Champion in the UFC.
Melendez is wrong though, they shouldn't leave the UFC to fight him. Edgar beat Penn twice, that triumphs anything Melendez has ever done.