That raises an interesting general question. What makes a new game in a series welcomed, tolerated, or reviled by fans of previous entries?
Assuming the later games are of the same or better quality as the first, what makes one game "a welcome update to a series getting stale" and another "a betrayal of everything that fans of this series have come to expect?"
Bearing in mind that love and hate for particular games are often highly subjective responses (to put it politely), I think it's possible to make some broad but useful observations. Here are some suggested categories of gamer sentiment regarding sequels:
A GOOD THING MADE BETTER
- Wing Commander 1 & 2 => Wing Commander 3 & 4
- System Shock => System Shock 2
- Thief => Thief 2: The Metal Age
- Uncharted: Drake's Fortune => Uncharted 2: Among Thieves
- TES IV: Oblivion => TES V: Skyrim
NOT THE SAME, BUT SURPRISINGLY GOOD
- Deus Ex => Deus Ex: Human Revolution
- UFO: Enemy Unknown (X-COM) => XCOM: Enemy Unknown by Firaxis
THEY DUMBED IT DOWN
- TES III: Morrowind => TES IV: Oblivion
- Deus Ex => Deus Ex: Invisible War
- System Shock 1/2 => BioShock
- Mass Effect => Mass Effect 2
YOU KILLED MY PUPPY
- Fallout 1/2 => Fallout 3
- UFO: Enemy Unknown (X-COM) => XCOM by 2K Games [tentative]
- Resident Evil 1-4 => Resident Evil 6
All of these are debatable in their details. I don't agree personally with all of them, and some of them many not even be accurate in an objective sense. But they do, I think, accurately reflect how these games are assessed by gamers generally. So for now, let's assume that you're willing to accept most of the category assignments I've proposed here. Some sequels are loved, some are accepted, and some get mostly bad press.
What do the games in each category have in common with each other? And what sets them apart from the games in the other categories?
One fairly obvious difference is time -- specifically, how much time has passed from one entry in a series to the next. Games that are perceived as improvements on their predecessors tend to be released fairly soon after the prior game, while games made much later tend to be judged more severely. Skepticism probably colors beliefs before a late sequel is released, and nostalgia for a very highly regarded earlier game makes a fair comparison harder for any follow-up. This suggests that it's a good idea to have a design for a fairly similar sequel ready to implement if the initial game in a new franchise takes off.
Slightly less obvious, and related to time, is who makes the follow-up game. A sequel made by the original game's creator (or members of the team that made the original game) is likely to be perceived more positively than a game made by a completely different developer.
(There are exceptions for a few studios. Knights of the Old Republic 2 and Fallout: New Vegas, developed by Obsidian Entertainment, while less appealing to some players of KOTOR and Fallout 3, received higher marks from many gamers. And Eidos's respectful handling of its Deus Ex prequel muted much of the negative discussion of its in-development Thief sequel. At worst, sequel games made by studios that early game fans feel they can trust fall somewhere between positive and mixed reception.)
Changing the display engine or target platform often generates some disapproval. This showed up in particular after 2000 when primary development shifted from the PC to the new generation of game consoles. Deus Ex and The Elder Scrolls are examples of franchises that suffered from this perception; Deus Ex: Invisible War and TES IV: Oblivion were developed first for consoles then ported to the PC platform of their original games, and are frequently given the "dumbed down" criticism by fans of the earlier games.
BioShock, though not a direct sequel to the PC-based System Shock games, also met with some of this criticism, but overcame it by creating a new and strongly-realized setting for the fairly similar game mechanics. BioShock also shows that falling into this category doesn't imply that the later games must be "bad," either artistically or commercially. Gamers lost to the "dumbed down" problem may be replaced by those who gravitate to or grow up using the newer target platforms.
A final factor appears to be whether a sequel makes significant alterations to the primary gameplay mechanics (and often the player visual perspective) associated with a popular franchise. The X-COM and Fallout franchises went through this -- fans of the pausable, tactical third-person format of the earlier games reacted very negatively to the shift to real-time, first-person shooter gameplay of the later games. Fans of Fallout 1/2 can still be found grousing about the change in Fallout 3 despite the later game's evident quality and popularity. Mass Effect 2 was criticized for significantly reducing the number of character skill options from the more RPG-like orginal Mass Effect. And 2K's as-yet-unreleased first-person shooter take on X-COM (which was recently revealed as having been changed to third-person perspective) generated more negative comment than Firaxis's more faithful recreation.
These effects are understandable, and maybe unavoidable. It's impossible for a sequel to perfectly please every gamer who enjoyed the initial game(s) while at the same time changing to attract new players. Gamers as a group are notorious for wanting "the same, only different." If it's too different, you lose the fans who liked the original game. But if it's too similar, you'll be criticized for "charging for the same game twice."
It's also creatively and financially risky to make too many trips to the same well without perking things up somehow -- consumers of any kind of entertainment will eventually tune out. Finally, from a developer's viewpoint it's just less fun to iterate on a well-known formula than to make a new game that stretches some different developer muscles.
Those realities acknowledged, it's also true (as Simon Ludgate recently pointed out) that if you're going to make a game that purports to be a new entry in a popular series, then your new game's design ought to at least include some core elements from the games that made the series popular. This is both a matter of courtesy and business: it does not pay to antagonize the people who are the biggest (and often most vocal) fans of the franchise you're trying to extend.
Finding the balance point between respecting the past while meeting new modern expectations is hard. But the reward for doing it well is gamer trust that translates directly into future sales.
Otherwise, just call it a "spiritual successor"....