@ExoDendrite Baseball isn't much of a thing at all outside of caps and bats, can understand why it got unreleased as interest overall is just too minor outside of Australia, Italy and Netherlands. Nintendo of Europe decided to release Disaster: Day of Crisis instead that wasn't released in the US as it was roughly the same time. Rusty's Real Deal Baseball on the 3DS was also unreleased, Nintendo Pocket Football Club got released instead. I don't think the Ken Griffey Jr. baseball games on the SNES/Game Boy were released either... Just checked, the first N64 one only came out in Australia but not Europe, the sequel also stayed in the US.

Even outside of Nintendo, it was really hit and miss on what baseball games got a release due to the lack of popularity of the sport and licensing issues. Sony's MLB The Show is either unreleased or in later entries, download only. A few of the 2K games were released, recall having both of The Bigs but MLB only got a few entries. Any baseball game that got a release in Europe and Australia were to pad out the library (Sega released a couple on the Master System and the Mega Drive got Super League but none of the World Series Baseball games or Sports Talk Baseball were released even if you could import the latter) or in the case of Acclaim, gave it a good shot with All Stars Baseball. Even the RBI Baseball series only had a couple of entries including the really good 94 and weirdly RBI 2 got ports to computers.

As strange as it sounds, probably didn't help that EA struggled getting baseball games out. It worked for Madden and NHL where interest was smaller or more localised (like Sweden and Finland for ice hockey) even if Madden skipped a few years and consoles but their NBA games were hit and miss (Lakers vs Celtics was actually recalled in PAL regions due to licensing...). At least basketball is more popular in Europe so not as much of an issue.

Relating to this Mario Superstar Baseball is one of the rarest GameCube games in PAL regions. NoE gave it a chance and probably had Super Paper Mario came out as intended instead of delaying it to be on the Wii, MSB would have got dropped. Frank "Big Hurt" Thomas Baseball is another rare game as well but don't recall which system...

Sorry for the lengthy comment, just mentioning the state of baseball games in general.

Unfun fact: This is the only Mario game on the Wii to have never gotten an official release in Europe and Australia. I've heard great things about this game, so it seems like they're missing out!

It misses a lot of stuff here, such as minigames, Toy Field, text & challenge mode in both english and japanese. also it misses the japanese banners, Character Logo & icons (Birdo is an example), Wii menu icon and Title Screen.