I usually run with: anything that allows you to develop a personality for your character and allows you to make decisions that affect the plot is an RPG.
Agreed...
Though, I'll take this a step further.
I think there's TWO elements that make a game a RPG:
1. The player must make decisions that can affect the outcome of the quest, game-world, and/or end-game.
2. The player can alter his character's very own base-statistics, class, abilities, skill sets, and/or equipment throughout the game.
Shadow of Destiny is an adventure game -- and it a;sp makes you make decisions that change the outcome A LOT -- usually by solving puzzles and deciding who to side with in dialogues. Many puzzles have multiple solutions. Problem -- Shadow of Destiny is really more of an adventure game, since you spend most of your time solving puzzles until the end of time. There IS nothing here based off your character's stats, skills, class, or anything -- it's about the player's skill of quick wit and how quickly they can come up w/ some logical answer to a puzzle. My character Eike will wind up like yours, in his looks, stats, and skills -- since he doesn't have any -- by the time the game's over.
Another one -- Silent Hill series. These games, more so than anything, are LINEAR action-adventure games. There's a big emphasis here on the action combat and puzzle solving (adventure) aspect of the game. Though, finding certain objects in the game or not finding certain objects, can really change the final outcome of the game, when the end hits. And there's numerous different endings, too -- it changes the ending drastically. So, is this a RPG? No -- it doesn't contain element #2.
If nothing you do affects the plot in any way and you have no way of developing any kind of personality for your character, it's not an RPG.
And yeah, I know there are a few that are borderline
So, yes Diablo would not agree w/ my rule #1, but it so does works with #2 -- BIG TIME. The game is literally packed w/ tons of skills, classes, abilities, and equipment. In likelihood, my Assassin will NOT look like your Assassin -- my character of the same class is likely going to be much different than yours. Also, Diablo is LOADED w/ tons of action -- so, that's why it's an Action-RPG. Sacred series would fit under this bill, as well.
Silverfall series treads the line even more so. It does fill both my rules. But, at its heart, more so than anything else, it's an action-RPG in the same style of Diablo. But, just about every quest, you have to decide to side w/ Technology or Nature. And your decisions will change not just the way the story turns out, but also the way your character's skills can be upgraded. Silverfall though is nowhere as deep as say many other RPG's in the decision-making aspect -- but Silverfall series are more of an RPG than Diablo, but nowhere as deep on the RPG aspect of rule #1 as say SW: KOTOR, BG series, Vampire: Bloodlines, NWN: Hordes, The Witcher, or PS:T.
STALKER: Shadow of Chernobyl is more so than anything else, first and foremost, is a shooter. Though, it does have, for the most part, an open-world at your disposal. Though, STALKER: Clear Sky blurs the line here and takes this a step further -- as now you can upgrade weapons and armor you already own -- which is a very RPG-like element. In these games, you can decide what factions to join; what missions to do and not do; which way to finish a mission; and it will all change the way the game ends -- especially in SOC. Clear Sky, regardless of what faction you are with -- the game only ends one way, since it sets up how basically SOC begins. Still, I'd consider the STALKER games shooters, myself.
