"Pseudo-sequels", spin-offs, loosely-connected games, etc...

[Gunstar Green]

Off the top of my head:

Metal Warriors is an unrelated spiritual successor to Cybernator/Assault Suits Valken.

The upcoming Star Citizen is a spiritual successor to the Wing Commander series in everything but name due to EA still owning Wing Commander. StarLancer was also a spiritual successor to Wing Commander.

A million shmups have spiritual successors. That would be a vast list in and of itself.

[Erik_Twice]

Japan got Pokemon Red, Green AND Blue for the gameboy America only got the Red & blue games

Not quite.

The original games were Red and Green. They sold very well and after a couple ROM revisions Game Freak designed Pokémon Blue, an updated release of the original games with slighty better graphics, noticiably in the spritework. It was only availble through mail order but it sold really well.

This Blue version was the basis for the western Red and Blue releases.

[ExedExes]

Metal Warriors is an unrelated spiritual successor to Cybernator/Assault Suits Valken

Even so, the Genesis got Assault Suits Leynos, which was Target Earth in the US

[ExedExes]

I'm gonna do some research and see if there's anymore NES or Game Boy games that fit this thread.

Here's a good one.

Battle Formula by Sunsoft (Famicom) ---- > Super Spy Hunter (NES) after Sunsoft gets Bally/Midway's license for it.

[BoneSnapDeez]

Can't forget the SaGa series, whose first three titles were released in the US as Final Fantasy games.

Makai Toushi SaGa (Final Fantasy Legend in the US)
SaGa II: Hihou Densetsu (Final Fantasy Legend II in the US)
SaGa III: Jikku no Hasha (Final Fantasy Legend III in the US)
Romancing SaGa
Romancing SaGa 2
Romancing SaGa 3
SaGa Frontier
SaGa Frontier 2
Unlimited Saga
Romancing SaGa: Minstrel Song

[BoneSnapDeez]

The Seiken Densetsu, or Mana, series.

First game was a Final Fantasy spin-off, then the series took off on its own.

Final Fantasy Adventure (Seiken Densetsu: Final Fantasy Gaiden in Japan, Mystic Quest in Europe - not to be confused with Final Fantasy Mystic Quest, of course)
Secret of Mana (Seiken Densetsu 2 in Japan)
Seiken Densetsu 3 (Japan-only *sniffle*)
Legend of Mana (Seiken Densetsu: Legend of Mana in Japan)
Sword of Mana (Shin'yaku Seiken Densetsu in Japan - remake of the first game)
Children of Mana (Seiken Densetsu DS: Children of Mana in Japan)
Dawn of Mana (Seiken Densetsu 4 in Japan)
Heroes of Mana (Seiken Densetsu: Heroes of Mana in Japan)

There are some Japan-only cell phones games too, but whatever.

Also, Square released the Western-developed Secret of Evermore for the SNES. Despite having a title similar to Secret of Mana, there is no relation in terms of plot, storyline, characters, etc. The gameplay is very much the same though - it's still debated whether this counts as a "spin-off" or not.

[Jmenglan]

Maken X is in the Shin Megami Tensei universe, love that game.

[BoneSnapDeez]

7 main Metal Slug games.

Metal Slug X is like an upgraded version of Metal Slug 2.

Other spin-offs include the PS2 Metal Slug, 1st Mission (NGPC), 2nd Mission (NGPC), and Metal Slug Advance.

[Damm64]

7 main Metal Slug games.

Metal Slug X is like an upgraded version of Metal Slug 2.

Other spin-offs include the PS2 Metal Slug, 1st Mission (NGPC), 2nd Mission (NGPC), and Metal Slug Advance.

And XX is a upgraded version of 7.

[prfsnl_gmr]

Maken X is in the Shin Megami Tensei universe, love that game.

I did not know this...Are there any new Japanese games that do not relate to the SMT universe in some way?

I keep expecting to see "Metal Gear Solid: Devil Summoner" or "New Super Mario Tensei: Strange Journey"...