Well, DK and Luigi aren't purely Western games. They are japanese licences that were developed by western studios which differs completely from being 100% western. Deleting them from this list and putting others would be more relevant in my opinion.
This was something I had to think about when making this thread: what exactly was a Western game?
I ultimately decided to stick with where the developer was based because when I thought about it, you'd end up with some really odd data points if you based it more on Intellectual properties or publishers. For example, Dragon Ball Z: The Legacy of Goku was based on a Japanese license, but the developers were American and the publisher was European. Further complicating matters is the fact that even many Western games that do well are published through Japanese publishers, but only in Japan. This was why the best-selling games published by Capcom on the PS2 were technically the Grand Theft Auto trio.
Ultimately, I chose to just focus on where the developers were based. It seemed like the simplest answer I'd find. If it's any comfort, I'm planning all including all games above a certain point, whether they are based on a Japanese property or not, so it's not as if any more Western games are being kept off the list by Donkey Kong Country.
Love and tolerate.