Zulu: Micheal Caine was second choice for role.
Easy Rider: Peter Fonda was second choice for role.

Not what I was looking for, but it does concern actors.

I changed the movies coz i thought my original choices made it too easy. You want the original movies as well?

Nobody wanted clues to make it easier but nobody made any guesses. Strange.

The original movies I was going to choose but thought they made it too easy were Flawless and Bucket List. I already told you it concerns the actors. I now expect the first person reading this to get the answer.

Poor Plugsy, he's so misunderstood.

MOVING ALONG...

The two movies are:

Return of the Jedi & Enemy at the Gates

Both feature Wookies?

Oh, wait...that's Ron Perlman. My bad.

Hint: they both feature a plot element at their climax.

In both cases: it's a trap!

Nah, the penultimate antagonist helps the hero overcome the big bad in a redemption-through-death self-sacrifice. Your go, Danny.

Lol, so long with no reply I'd stopped looking and forgotten about this thread. So the answer was both had an actor in who'd been oscar nominated in each of consecutive decades.

I figured once I picked films where they were both the star and they are the only two actors to achieve that then it was obvious. Guess not.