Is this guy in every sci-fi fantasy movie?

There is always a guy with long platinum blonde hair where it’s perfectly straight and hanging down his back. Every. Movie, or am I imaging things (again)?

You mean like Lee Pace in the Hobbit?

That’s him. I’m pretty sure the prototype was one of the baddies in Die Hard.
Wasn’t there one in Dune?

And, Lee Pace is playing Thranduil, the father of Legolas, who also had that hairstyle:

Plus, there’s Thor, of course:

David Bowie in Labyrinth. Not platinum blonde, but in the area.

Isn’t there one of these guys in some of the Star Wars movies?

The only major male character I can think of, off the top of my head, with that sort of hairstyle, is Qui-Gon Jinn, but he had dark hair.

Lucius Malfoy

The baddie from “Hellboy 2: The Golden Army”

And the chief Morlock from the 2002 remake of “The Time Machine”

Cheating a bit as it’s not a film, but Link from Zelda surely fits the bill?

Shoulder-length upswept strawberry blonde isn’t remotely the same “bill” as straight platinum halfway down the back.

Thor doesn’t meet the description, either.

Don’t forget these guys in the Matrix sequel:

The archetype has been around a long time.

The Dreaming City was published in 1961.

But is the character described in-story as having long straight pale hair? If not, when does that cover art date to?

IIRC, he’s an albino, so certainly pale at least.

As @Chronos notes, Elric is an albino, so white hair is assumed. I can’t speak to exactly how his hairstyle is described in Moorcock’s stories, but in 1980, he was depicted in a Dungeons & Dragons rulebook (the first edition release of Deities & Demigods) , and here’s how artist Jeff Dee drew him:

Here’s one from 1979:

Here’s one from 1976:

Elric is a very popular figure in fantasy artwork. Those are two pictures I managed to date, but there are many, many more. He’s always depicted with long white hair.

Well sorry i spoke!!

Don’t forget Daemon Targaryen, from HBO’s House of the Dragon, whose character design was a blatant Elric ripoff: