Diablo: You play the role of a hero destined to defeat the armies of Diablo in combat. The player has input into the equipment they carry and the attributes they train. Random quests are provided along the way, mostly combat related. I'd be hesitant to class this as an RPG. While you can develop and arm your character in any way, you ultimately have to use your class' one specific strength to win.
Diablo 2: You play the role of a hero destined to (again) defeat the armies of Diablo in combat. Given this restriction, you have an abundance of ways to complete this, namely in the skills you decide to learn. I would class this as an RPG as you have input into the how the game is completed within the boundry that it must involve combat.
Divine Divinity: You play the role of an unknown who rises up to be the Divine One, saving the world from the Lord of Chaos. Moral and ethical dilemas force you to take sides, both of which have their benefits. Many of these decisions afect the game later on, even if only minutely in most cases. I would class this as an RPG as your decisions noticably affect your reputation and other parts of the world.
Counter Strike: You play the role of a SWAT officer or terrorist where you must complete your goal within the time limit. You have a selection of weapons and, as a team, a selection of positions within the team (defence, offense, tech, etc.) I would not class this as an RPG as your actions only mean anything for a measly five minutes. Having only one goal in the game means your actions never affect anything except whether you win or lose.
Indiana Jones and the Fate of Atlanits: You play the role of Indiana Jones as he tries to prevent the Germans from taking over the world. There are three unique paths through the game. I would not class this as an RPG as each path is simply a series of one answer only puzzles.
The Sims: You play the role of a family. Each family member can be developed and trained. Relationships and jobs are also dynamic. I would almost class this as an RPG. <ducks for cover> The family members daily lives can affect them for the rest of their lives, but ultimately, everything is reversable, except for death.
Generic Soccer Game 213: (Sorry, haven't played many.) You play the role of a soccer team. Your goal is to become the world champions by defeating more teams than any other team. Your team members improve with experience and star players can be bought. I would not class this as an RPG as the only way to win is by getting the ball in the net. However you develop the team, the next challenge will always be the same.
In summary, my view of an RPG is one where you can noticably change the future through your decisions. If you only have one main option, then you're not really making a vital decision. In real life, whatever you do in the role you live has lasting effects. For every mistake you make, your experience grows, but the world changes as per your mistake. Now after making that definition, I'll look at one more game:
Final Fantasy: You play the role of a hero and friends as they save the world from destruction/slavery/etc. by an evil villain. Your characters gain experience and levels through the game. I would not class this as an RPG as the story is strictly ridgid. You never decide anything aside from who to use next in combat. Now I know that anyone would class this as an RPG – and frankly I'd agree – but I have always seen them as a strategy game with a compelling story more than an RPG.
Of course, these are all simply my opinions from my own perspective.
@Virgo_Bluefire, please duck for cover after suggesting that Sci-Fi's cannot be RPGs. <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" /> I'm a big fan of Cyberpunk and Sci-Fi RPGs.
@Alrik, I don't think that experience points and upleveling are strictly necessary for an RPG. They help in that you can develop and attach yourself to your character. But if a story was written well enough, your characters decisions alone could make it an RPG, and simultaniously could attach you to your character.
