The way they should make sequels for many game series-
There should be as much difference between the games as the gap between Metal Gear Solid games.
MGS1: Gizzled veteran sent into nuclear disposal facility to retrieve hostages and stop a nuclear strike, gets dragged into tangled web of evil ploys by multiple people. Set in a non-existant island off the coast of Alaska in the middle of a snowstorm.
MGS2: Gizzled veteran is framed for a terrorist attack, rest of game follows a character expressly intended to deconstruct an alleged power fantasy the first game provided players. Set on a massive oil spill cleanup facility, and referenced the first game frequently in ways that could be considered sacriligious. Ending incomprehensible to anyone but the development team (but I liked it). Introduced a first person aiming mode, shooting around corners, destructible lights, holding up guards, and the tranquilizer pistol, all of which became series mainstays (except shooting out lights, curiously enough.)
MGS3: Set in the 1960s, develops a villain from the original MSX2 game series into a sympathetic, relatable protagonist who gets screwed by both superpowers during the Cold War and is sent on a mission into a remote Russian jungle to kill his former mentor. Completely changed gameplay mechanics to allow the player to camouflage into the surrounding environs and introduced a grappling hand to hand combat system. Also used a more realistic healing system, requiring Naked Snake to use medical supplies to operate on himself to heal his wounds (splints and bandages to treat broken bones, cigar to burn off leeches, etc.)
MGS4: Set back in the future, gizzled vet from MGS1 is sent on a mission by his CO from the first game to kill a villain that’s been in the series the whole time backstabbing just about everyone he’s ever met (even in MGS3 as he was learning his craft). A natural extension of mechanics from MGS3, the player could camouflage to any texture in the environment, the hand to hand combat was more controllable, and a whole new in-game economic system was added for the purchase and modification of weapons and ammunition. Set in locations across the world with impressive visual variety and diversity of gameplay (with exception of Act 3).
Connections between games:
-The plot interconnects all of these games with a nigh-incomprehensible web of conspiracies, characters, and motivations, that literally requires a freely available encyclopedia from the PSN to keep track of from game to game.
-The cutscenes. Well directed, voice acted, and consistently entertaining. By MGS4, however, the cutscenes are getting to be epic length diatribes of such complexity that some gamers who are less story reliant will be driven to self-harm by their sheer length. Film majors like me, however, have plenty to geek out over, as each game’s cutscenes approach film quality looks in terms of their emulation of cinematography, incorporating zooms, whip panning, a handheld look, filters for color correction, dirt and water hitting the lens, slow motion, occasional fast cutting, and other such elements.
-Series regular Ocelot backstabbing absolutely everyone he’s ever met, in pursuit of inconsistent goals.
In other words, consistently refining and reinventing the series as it moves forward.