I think what made it the "meme anime" was that Evangelion was the first anime to really go all-out on merchandising. You could get evangelion curry. With sonic that's kinda funny, but when the anime is some weird spiritual allegorical thing, you get kind of a whiplash. Going from watching Shinji "god I'm so fucked up" to seeing them all smiling on a pack of oreos is jarring and kinda funny. It made people on the early net post the merch and share pictures of it, which led to making memes about the merch, which led to memes about the show itself.

But that's just a theory