I was just thinking about how it was odd to me, starting with Metroid Prime on the Gamecube that future Metroid games mostly had the word "Prime" in their title. Like why did Metroid Prime pinball have Prime in the title and not just called Metroid Pinball? Was it because of re-used art assets from Prime 1 or something? Perhaps it takes place during, right before or right after the storyline in Metroid Prime? Just speculation. Why didn't Metroid the other M have Prime in it's title? There was also Metroid Prime Federation Force that was a Prime-Branded title that was quite different than Prime 1-3. I feel like I just don't know enough about Metroid lore to understand the titles.

For a lot of people, metroid prime was their first metroid game. The series had been around for years but the prime series was intended as an introduction to a newer generation and was given the "prime" tag to distinguish it from the earlier 2d titles as something fresh and new for current gamers. Metroid prime pinball was likely called prime for the sake of continuity considering that all the other metroid games of the time were called prime as well. Metroid fusion and metroid zero mission weren't "prime" titles because they adhered to the 2D roots of the other older non prime games like super metroid. Other M was meant as a modern metroid game that appealed to fans of the older metroid games and thus "prime" was omitted from that as well. Also the prime series, at least 1-3, while having different settings and plots, have connecting elements to bind the series together. So yeah I think, but I'm just a kitchen fitter so don't take that as fact

Ok, so why didn't Metroid Fusion carry the "Prime" moniker? It came out around the same time as Prime 1 and even had some save transfer functionality via that overpriced GBA cable.

Because it was a 2D tradional Metroid game I guess. Same as Zero Mission that came out around the same as Prime 2. Prime started a new storyline of their own that Fusion wasn't connected with, despite the linkup capabilities

I was always under the assumption that all the Prime games were FPS titles, while the others weren't.