My thoughts:
Role playing is playing a role of someone else. Technically, playing an Indiana Jones game is role playing - you're playing someone else. But in Indiana Jones, you play like Indiana and think like Indiana and talk like Indiana. You're not so much playing a role as playing someone else entirely with minimal character input.
I see Diablo as a role player. The game offers you the chance to become a champion against evil through combat. That is the scope of the game. If you don't like it, don't buy it. You can select your class and develop it to your tastes. Each specialised class in Diablo 2 can be refined further, each having roughly three distinct paths, depending on your tastes.
Divine Divinity offers more with reputation, quests, multiple responses to NPCs... While a lot of actions don't have a great effect on the overall game, it's all part of your character. The Divine One could be the most holy and giving person in the world or an evil greedy [nocando]. All the same, you go and kill the ultimate evil. It's all about what you want the character to be. Be something you're not. If you have fascinations of mass murder, it's better that you play it out in a game then in real life!
One final game: Nethack. A standard dungeon crawl with the addition that when you die, your save game is deleted. There is an abundance of actions that you can perform. When you finish a game (successfully or fataly), the game lists a number of statistics: were you a vegetarian, did you comit genocide, did you pray for divine intervention, did you use a weapon, did you polymorph...? These are all role playing options which ultimately come down to this little statistic panel. They're there for you to increase your game difficulty through self deprivation. So as a vegan, do you sacrifice your vow and chow down on the goblin corpse or do you stay true and starve to death? I think moral dillemas like that make for better role playing role playing.
