Were the Sevii Islands meant to be the Video Game equivalent....

They never mentioned Sevii Islands in the anime.

I've been to Route 14, and I never saw SeaGallop.

SeaGallop might have other destinations than Sevii.

Someone in the game (And therefore this is canon) said that the Sevii Islands were far south of Kanto.

And then there's Pokemon 2000, with Lugia, and Navel Rock, with Lugia.