Game sequels usually follow the same strict continuing structure as books and films. Sometimes they don’t have anything to do with each other except the names and general overall idea. The only continuity as such is just there, not really doing anything. In most cases plot is the thread that connects everything together, even in video games for better or worse. As games are a generally an interactive form of entertainment as opposed to more traditional mediums, they can, could and should convey continuing playing of one series from instalment to instalment.
How this continuing game then could be made? Before memory cards it was downright impossible to do on consoles and arcades machines. With the invention of memory cards the same method can be done on consoles, and to some extent with arcade machines as well; the save in one game carries some significance to the other. This is a balancing act, as putting too much emphasize on the saved data will always push out new players.
The Second Super Robot Wars Z; Chapter of Rebirth, or SRWZ2.2 Saisei Hen, puts it so that some already obtained skills carry over from the previous game, but nothing that truly makes a large difference. It mostly rewards returning players with continuity so that their effort in previous game does not go to waste. Similar thing was done in an earlier SRW game, Super Robot Wars F and F Final, where character levels and skills would directly jump from the previous game to other.
This is good kind of continuity. It rewards the player to start from the first one because it has impact on the later game. It’s not too overt that it would push new players away and keeps its doors open.
Mass Effect, while looks really good on paper with player selection carrying over, does things a bit wrong. The selections, player’s own character and all that carries over and that’s good. However, nothing else really does. The player still starts basically from naught. He might as well start a new game, because the ending in Mass Effect 3 doesn’t really fetch will to play the first two parts. Then again, the amount of game play and story in Mass Effect games is completely bonkers and some mechanics are more or less completely horrible and broken. Well, PC games and their emphasize on story…
Game saves could always play a bigger role. I’m not talking about story elements because those don’t matter. I’m speaking of affecting mechanics and gameplay. While truly either, the way Metal Gear Solid digs up save data and displays certain deviations according to that shows that this gimmick could be more. For example, imagine if you had all of the Mario Sports games saves on your memory card. Every game could read what saves you’ve got there and open some interesting hidden options etc and add player outfits or the like. Still not really gameplay effecting stuff, but it would show a link between the games.
RPGs are the biggest genre that would benefit from save continuity. For example, player’s characters would carry their experience, weapons and so on from a game to another. At least Legend of Heroes; Trails in the Sky is known to do this. This would affect how the game is played initially, as well as giving a complete continuity between the games rather than doing Metroid’s way and making the player start from the scratch, even if this doesn’t make sense in the story’s narrative or setting. It’s keeps the continuation cohesive from game to game, and adds some content and credibility.
I’ve been talking a lot of story continuity and all that even thou they do not matter in the end. However, it has to be taken into account, as even the simplest stories have to have credible cohesion. Mega Man Zero and Zero 2 have nice cohesion and neat tricks linking the two games. Initially the in-game menu screen resembles the first game’s screen, but battered and broken with unfunctioning weapons. After the intro stage the game updates the menu screen with a new sleek look and the doctor fixes the weapons, as well as modifies one. Neat and done without save transferring. It wouldn’t be hard to do this in any sequel, but it’s never made. It adds to the game world those little things you notice and like.
Another game series that uses extensive save unlocking is Xenosaga. It mostly unlocks swimsuits to the characters or the like, but it adds to the game. Sometimes the swimsuits are actual items that can be worn in-game and have decent stats for a new game, or are just for fanservice. Most likely for both.
Now the question is why to do this kind of thing at all? First of all, it adds to the game’s world and content, even if little. Players with completed save data are rewarded of their loyalty and efforts for the game, and new players most likely will get interested in the previous game as well, thus gaining a new, perhaps even loyal customer to the company. A customer is more important to a company than anything else, at least it should be. While the method how the game recognizes a previous save is easy, but what it does and balancing the effects is always a bit harder, but that’s what the game designers and programmers are paid for to do. To deliver us a good game that we, the customers, want.