Games that interact with other game's saves.

[ignition365]

I may not have worded that right.  But I'd like to compile a list of games that read your memory card, hard drive, or the cloud and look for saves from other games.  It's sort of a unique feature that isn't used that often.  I can't seem to find a list of such a thing on the internet, but maybe I'm not using my google-fu right.

Games like Metal Gear Solid where it would look for other Konami games and read your god damned mind.  Games like Mass Effect that import your choices from previous Mass Effect games.

Off of the top of my head

Metal Gear Solid
Mass Effect 2
Mass Effect 3

This whole topic came to my mind because I own Winback for PS2 and Winback 2 for Xbox, but I can't find any info on whether or not the game does such a thing (I'm sure it doesn't).  Since it doesn't, or likely doesn't, I won't bother getting Winback 2 for PS2.

[anagar]

I know the Naruto series does, the saves unlock support characters and gives money.
The Ratchet & Clank Future saga, first game save gives discounts in third game. (Not sure for Quest for Booty)
Hatsune Miku Project Diva F/F2, Items from first imports to 2nd.


That what I can come up with from the top of my head for now.
 

[rayne315]

all .hack games in their series import your character file to the next in the series.

Im not sure if this counts but undertale stores information outside of the save games to keep track of if you have killed anything. this follows through to deleting your saves but not to deleting the game.

[abe]

Rosalina is unlocked more easily in Mario Kart Wii if you've got Super Mario Galaxy save data. I can't really think of any other examples off the top of my head that haven't already been mentioned.

[mrfoxhound]

all .hack games in their series import your character file to the next in the series.

Im not sure if this counts but undertale stores information outside of the save games to keep track of if you have killed anything. this follows through to deleting your saves but not to deleting the game.

You beat me to mentioning the .hack games. A lot of DS games such as Mega Man Zero collection and Mega Man ZX read GBA save data when putting Mega Man Zero 3 into the GBA slot.

[metshael]

The Suikoden series comes to my mind, you can have two more characters in Suikoden 2 if you have a save from Suikoden 1, you can unlock two more scene for the theater in Suikoden 3 if you have a save from Suikoden 1 and Suikoden 2 on your memory card, and the last was Suikoden Tactics (or Rhapsodia) where you can recruit two more characters if you have a save from Suikoden 4.

[shfan]

Samurai Warriors 4 Empires will unlock a banner each if Samurai Warriors 4 or Samurai Warriors 4-II save data is present on your HDD.

[matimo]

Pokemon black 2 White 2, that's all i can think of atm. ._.

[telly]

I think the Need for Speed games interacted with each other in some way on the PS2, I don't remember how though 

Also Silent Hill 3 has unlockable data and scenes if you have a completed SH2 game on your memory card.

[jeffmandm]

I know that some of the 2004 season EA Sports games have a special feature called EA Sports BIO, which allows you to keep track of stats between games and, with the case of NCAA Football 2004, import a custom player or NFL draft class into Madden 2004. PS2 and XBOX owners also have the ability to import a NBA draft class from NCAA March Madness 2004 into NBA Live 2004. I don't think MVP Baseball 2004 uses EA Sports BIO, and neither does NASCAR Thunder 2004.

LEGO Star Wars II: The Original Trilogy actually uses something like this to its advantage: if you have a save file for LEGO Star Wars: The Video Game on your PS2/GameCube memory card or XBOX/computer hard drive, you can unlock and buy a cheat allowing you to play as characters from the first game in the Original Trilogy (minus any character already in the Original Trilogy game, i.e. Leia or Antilles). While this is redundant since The Complete Saga is a thing, before complete saga came out this was the only way you could play as the prequel characters in Episodes IV, V, and VI.

[desocietas]

Hm, I know what OP is talking about where in Metal Gear Solid, one of the characters will read your character's "mind" in a sense by checking your memory card and mentioning what games you've played and how many times you've saved in your game thus far.  Pretty spooky for folks who weren't expecting that trick.

[mrfoxhound]

Hm, I know what OP is talking about where in Metal Gear Solid, one of the characters will read your character's "mind" in a sense by checking your memory card and mentioning what games you've played and how many times you've saved in your game thus far.  Pretty spooky for folks who weren't expecting that trick.

Mhm. Psycho Mantis. Scared me as a kid. The conversation with Meryl before the fight with Mantis is how I got my username.

[aliensstudios]

The Dragon ball Z: Budokai series lets you unlock hidden characters in two and three for having saves on the memory card

[badATchaos]

Pokemon Stadium could teach your Pikachu Surf. (A move Pikachu can't normally learn.)
Pokemon Ruby and Sapphire could receive a patch by connecting to Pokemon Box, FireRed, LeafGreen, Emerald, Colosseum, Jirachi Bonus Disc, or Pokemon XD: Gale of Darkness.
Cities made in SimCity 2000 could be loaded in SimCopter and Streets of SimCity.

[kashell]

The Xenosaga series took advantage of this. Having data from Episode I would unlock some costumes in Episode II. Obviously, having data from Episode II would unlock costumes in Episode III.

The Talesseries started doing this, too. When you start Tales of Symphonia Chronicles on the PS3, the game will read your hard drive to see if you have any other Tales games saved. If you do, you'll unlock some really awesome Tales-related costumes for your characters. The same happens with Xillia 2.