I loved the books, especially the Fall... I have to say that the ending of The Night Eternal just felt entirely half a**, though. I don't like drop off endings, and that is all that it was.
I have to give Hogan and Del Toro credit, though, because I haven't found a vampire book in years I genuinely loved. Typically I'll read maybe 30-50 pages a night, and this series (The Strain Trilogy) had me reading 100-150 pages a night and wanting to stay up even later to continue reading.
In regard to Del Toro and Hogan recycling from Blade 2, stealing (or so it seems to be implied here) material, or just being generally similar to other stories-- It's going to happen. Compare King on any level to Lovecraft and the similarities are astounding. My favorite example would be Lovecraft's The Rats in the Walls vs. King's (Jeru)Salem's Lot... It's not a matter of similarities sometimes, it's a matter of how cleverly a similar concept can be used and blossom into something different... Which does occur with the vampires in The Strain trilogy in book 3 The Night Eternal.