OMG, I am legitimately shocked to know that people will watch a sequel to a movie before watching its predecessors. With that said, please do not do that with the Blade trilogy, because Blade Trinity is the only one NOT worth watching.
Blade Trinity did not live up to the standards of the first two because they strayed from the formula; Blade was a successful vampire hunter/slayer because he had all of a vampire's strength, and none of their weaknesses. So I, like most, was confused by Jessica Biel aka Whistler's daughter. How and why was she such an effective vampire hunter/slayer? It made absolutely no sense!
Furthermore, she was not a character anyone knew, so it was a bit insulting to have simultaneous scenes of her fighting beside the Blade character; no one came to see her, we came to see Blade. It was as if the studio was trying to make a new character at the expense of sacrificing Blade.
Then there is Ryan Reynolds playing the exact same character he plays in every film; that man does not wear many hats. I found the film nonsensical, and boring with a weak plot. Wesley Snipes and the actor who played Whistler were very disappointed in the direction the studio chose to go, and it was reflected in the acting.
Do not waste your time on this film.