Mr Morden asked the same question "What do you want?" to the Narn, Centauri and Minbari representatives on Babylon 5 in Season 1. These are the major species on Babylon 5. Yet, why didn't he ask the humans, given that humans are in charge of Babylon 5 and are arguably the most important species on Babylon 5? How could humans be missed out? As a member of the human race, I feel somewhat left out and unimportant.
Because in the episode where Morden goes around asking the ambassadors what they want he is intercepted by Kosh before Morden gets to Sinclair and Kosh tells Morden,
"They are not for you."
JMS confirmed online that "they" were humans. (Source) Being warned off by a Vorlon was enough for Morden. But the Shadows obviously made contact with other powerful humans at some point, such as Vice President Clark and Psi Corps