Is this the movie that started it all?
Before Blade was released WB made big budget Superhero movies, and all Marvel made was made-for-TV garbage (Dr. Strange, Spider-Man, Captain America, Captain America II, The Trial of the Incredible Hulk, The Death of the Incredible Hulk, Nick Fury: Agent of Shield).
(Edit: When I first wrote the above I forgot about Howard the Duck and the 1990 version of Captain America, but both of those on further illustrate my point.)
Starting with Blade, Marvel has released 28 major motion pictures based on Marvel Universe characters by my count, 7 of which grossed over $300M in the US alone. In the same time WB has only released 7 DC Universe theatrical films--9 if you count Constantine and Watchmen, and only 2 of those surpassed $300M.
I think 1998's Blade marked Marvel's turning point just one year after 1997's Batman & Robin foreshadowed bad times for DC.