I've seen this question go around,and I've decided to give my opinion.Well obviously an RPG is a ''role playing game'',but in most games you play,you play the role as some sort of character.

Some people say RPGs can be defined as games with levelling up,character customization,and allowing you to make decisions that affects how the story turns out,but God of War and the GTA series allow you to level up so why aren't they refered to as RPGs? Some people say because the levelling up in God of War and GTA is very minimal,but the same goes for many games that are refered to as RPGs such as hack and slash RPGs such as Baldur's Gate Dark Alliance,Champions of Norrath or first person RPGs such as Fallout 3 and ES III and IV.

In fact GTA San Andreas has quite abit of character customization,you can level up specific stats such as strength by working out at the gym,or speed by running around alot and you can modify clothing and hair s t y l e

Final Fantasy games don't give you very many choices in how you want the story to turn out,in Final Fantasy VII you could ''choose'' who you wanted to go on a date with,but it was deliberately set up so most likely you would go on a date with Aeris,unless you tried very hard to give another character alot of attention so you could go on a date with that character.And at the diner you had 3 choices of what you want to tell the chef about his food(whether it tasted good,OK,or like dogfood),and you can buy an apartment in a tropical resort and play the video games at the arcade and ride on the rides at the amusement park,but in Harvest Moon you can choose you want want to marry,and you already own a house but can buy a business but HM is regarded as a real life sim.But Fable is regarded as an RPG because is has very basic levelling up,and you can get married and buy a house?

Character interaction I've noticed is another common thing in games that are regarded as being RPGs,for example in Star Wars KOTOR and Jade Empire you can choose from alot of different dialogue to say,and the other characters always have a story to tell you or information about the world,and you can choose which stories or information you want to listen to and reply to it in a respectful tone or you can be rude to them,and you can even flirt with people.But in Final Fantasy games,the other characters mostly say 1 thing over and over again and you rarely have a choice of what you want to say to another character.For example in Final Fantasy games,you can't walk over to another character and ask them to explain a story about something to you,or any deep information about the world,the character will mostly say a 1 line riddle.But Final Fantasy games are still regarded as an RPG.

In GTA San Andreas you can openly interact with people such as insulting some random person on the street(calling a woman walking past a ''ho'') and you can go into fast food resturants and buy food,and you can go to a barber and get a new hairs t y l e or you can do an armed hold up in a store.

I've thought before,that RPGs are story based games(because many Final Fantasy games are more about their story than the actual gameplay)but there's many games that are regarded as RPGs that have minimal story and mostly based on gameplay such as Baldur's Gate DA and Champions of Norrath.

Perhaps an RPG can be a game where stats come into things and a dice roll system for combat is used.Every RPG I can think of,whether it's turn based,hack and slash or First Person uses some element of luck for combat.eg in Final Fantasy games sometimes you can land a critical hit on an enemy which does alot more damage.Sometimes when an enemy attacks you they can miss if your evasiveness stats is high.In Elder Scrolls III and IV,you can swing your weapon at an enemy and miss even if the enemy is just standing there because there's always a chance you'll miss with your swing or they will dodge your weapon(but it's a random chance,the enemy doesn't do it manually).

To sum things up,I don't think there's 1 real definition of an RPG,and they are a combination of different gameplay elements and the same thing goes for games from different genres.Halo has some 3rd person shooter elements such as when you use vehicles or turrets.The only 1 thing I've noticed every RPG has is some element of luck(so there's a dice roll s t y l e system in there somewhere)where as in a FPS if you lock the target onto an enemy and shoot,your bullets will always hit them unless they manually dodge it.Same thing is in GTA when you lock onto an enemy and shoot,the bullets always hit them and there's no element of luck that the bullets can somehow miss.