The biggest in NL is the Amstel Gold sportief.
One of my Sunday morning cycling pals is Dutch, he always goes back for this one, either as a participant or spectator. The main benefit of the later is you get to drink beer all day. But you don't get to cycle as much.
In a mad moment, I entered the lottery for the 260km route. God knows what I'm going to do if I actually get a place!