Hmm Elite Explorer for me is:
-Having discovered at least one of each of the possible astronomical bodies that exist, from O stars to Herbig objects to Black Holes to Carbon Stars...etc.
-Having mastered the Galaxy Map and the regions of the Galaxy. Think you should generally know where something in the galaxy is (e.g. should know where Sag A is, where the Great Annihilator is, a notion of where the most popular nebulae are, etc.)
-Having deep understanding of the configurations and modules more beneficial for exploration. This also happens to increase understanding of your ship greatly, not only for exploration.
-To have had at least 3 formal exploration trips (10k ly and over, round trip)
-Run a major exploration/research, creating hypothesis, follow thru with observation and results, and present findings to the Explorers Community. This is like presenting the paper to get your graduation. I know, you don't have to, but this is my idea, and I did so. Gave me a sense of accomplishment as Explorer.
-Make a major collaboration to the community in terms of service or findings or making constructive and helpful insights/comments/information.
-"Making money, money, money tons of it, hahahaha, become rich to own them all! all! all! That's the purpose of exploration!! to be the richest man in the world!!!" <---said no one. Ever.
Purely having 160 MM by exploring might make you Elite but I believe I read somewhere else, is not the only way, as someone reported getting there much earlier -at 120 MM. I guess is actually a balance between that and actual systems visited or some other metric.