An odd trend I've noticed on these boards in regards to the "Red Dead" series is how many people either ignore or forget the first game Red Dead Revolver.  Whenever the next entry in the series comes up calling it "Red Dead Redemption 2" or "Red Dead 2" are the most common place holder titles.  I cannot say I've ever witnessed this with any other series.  Can you think of a series where an entry is just forgotten like this?  Where a significant group of people seem to assume the sequel is the starting point or only game in the series?

Persona?

People jumped in late. It didn't explode like it's sequel but that happens. If GTA III or SF2 didn't have a number at the end, they'd be in the same boat.  Even Call of Duty Big Red One.

Well I can't remember any others.

What was that game before Halo? What was that game before BioShock?

(I'm good at this)

I choose to ignore it because I never played it.

However we are right in calling a new game red dead Redemption 2 or red dead 2 because the second game wasn't numbered as 2.

Like it went gta 3, gta vice city, gta San andreas. We called the next gta 4 not gta 6 so go figure.

Hmm... I remember my dad playing it but I never played it myself. Are there any characters or storylines that start in revolver and continue in redemption? I always thought of it as more of a standalone title in the same world or something.

Not sure if I get what you trying to say with that example.
Call of Duty 2: Big Red One is a console spin-off. It didn't reinvent the franchise, it wasn't the game that came before the game that reinvented the franchise and, while obviously forgotten, it wasn't really a major game (RD Revolver wasn't either though).

If the second game wasn't numbered why would you number the third one then?  Shouldn't it be "the next Red Dead"?

My guess is it will be called Red Dead Re-something as numbers have not been in titles.

GTA had a GTA, GTA2, GTA: London, GTA3, so was an established numerical order as well as sub titled entries between numerical ones.

Has there ever been a game series that had two entries with subtutles and then the third entry was "the second subtitled entry 2"?

Don't know if this counts but

Metal Gear -> Metal Gear 2 -> Metal Gear Solid -> Metal Gear Solid 2

Super Mario 64 -> Super Mario Sunshine -> Super Mario Galaxy -> Super Mario Galaxy 2