Metroid Prime games always had very detailed visuals, but none of them was released on a HD console. The Wii U was Nintendo first console to have HD graphics, but unfortunately it didn't receive a Metroid Prime game, so we never had the chance to see what it would look like in a more capable console than GCN and Wii.
As we all know, the Switch is considerably weaker than PS4 and XB1, but it's still considerably stronger than the Wii U, which was much stronger than the Wii. That didn't stop the Switch of having it fair share of realistic looking games, like Doom, NBA 2k18 and L.A. Noire remaster, with Wolfenstein II and ARK coming as well. They are all downgraded ports of course, but they still look good.
My point is that even with the Switch not being able to push the same graphics as PS4/XB1, it can still run games with high detailed graphics, and it's a gigantic improvement in power over Wii and 3DS, so I'm confident that Metroid Prime 4 on will look vastly superior to Metroid Prime 3, with realistic graphics in the vein of other current gen AAA games, hopefully with a great art direction, so it don't look dull.
Edit: When I say realistic, I don't necessarily mean photorealistic graphics, like Crysis, which by the way would also be possible on Switch. It can be realistic but also stylized, like the previous Metroid Prime games.
"lupus in fabula, venit enim ad me."
Translation: I will always hate Fox for canceling The Exorcist.