I don't see why not. They were produced by a japanese company (although only partially). But if you don't want them to be, then they are not. In the end it all comes down to personal preferences, where no one can be wrong.

i guess that depends on how pedantic we want to be.

the last unicorn was animated by a japanese company, but written and directed by us americans. original voice performance was also done by non japanese people.

so if we say that a anime has to be a animated movie made by japanese people, then no, the last unicorn is not a anime.

if we say a anime is a animated movie where japanese people were responsible for the animation then yes, the last unicorn is a anime.

if we say anime is a genre descriptor and not a geographical label i wonder if avatar the last airbender or the castlevania animated series are anime and how ghost in the shell and my neighbor totoro both fit in their.