AVEE'S PROFILE

Here are some tips that work well for me.

The hero's motivation/reasons to get out of his daily life and start traveling and fighting baddies can be internal (i.e. to have a personal goal he wants to reach) or external (i.e. to take revenge on the evil murderer, to be forced to do something for someone else).

Then set a "flavor" to the selected reason: is it social, psychological, biological, etc. Let me set some examples here...

I think most cliches use external + social reasons such as: to save the world for the sake of mankind, to retrieve the crystals to prevent the planet's decay. These reasons are easy to think of and help build a world full of NPCs and different quests, thus they're widely used in all video game types.

Personal + social reasons examples: to rise through the military ranks and become number one, to retrieve the crystals to rule the world.

Psychological reasons examples: a princess trying to flee from the pressure of royal duties, a man's dilemma regarding his current relationship and a new flame (as in Catherine ^^)

Biological reasons examples (these might be tougher to think of): young wolves challenge each other to a test of strength to determine the next leader of the pack, a survivor of a plane crash tries to find food, water and a safe place to spend the night.

Of course you can have multiple reasons for a single character to embark on a quest. Try to be creative and combine reasons with the game's style (fantasy, horror, sports, etc.) Hope this can help ^^.

I second Speed Grapher and I add GunGrave the Anime Series: it is an emotionally deep story of best friends rising through the eschelons of the mafia. It is so gripping it almost made me wish I was among them.

This.

I'll try to reply to more comments, give me some time, but for now I want to ask you this:
Can we say a game has replay value only if there is permanently missable stuff in terms of story branches or customization, forcing you to start a new game to take a different path?
If a game offered a single path and an all-linear experience, could we say that this game has replay value if, say, the storyline is so great you want to start over just to watch it a second time?

I myself find it hard to decide whether or not a game has good replay value to me:

For instance, I've played one character's scenario in Saga Frontier and chose to learn some magic spells and battle skills of a certain type... yet I never had much interest in playing that game again, watch the other scenarios or learn different abilities. Saga Frontier is considered as having great replay value so, is it just that the game doesn't appeal much to me?

And then I played GunGrave 4 or 5 times, not because I think the game is particularly good... it actually is pretty bad. I played just to watch the cutscenes. The storyline and screenplay are so good I didn't bother at all fighting through the boring and linear levels just to watch them over and over again. So can we say that such a game has good replay value?

Or maybe the definition of replay value is still unclear... What do you guys think?