I wrote a 5,000+ word thread that was devoted to being the best and most compact quick-reference guide for writers who felt like they wanted to get a little cleaner on the various aspects of writing. (EDIT, found here [http://www.escapistmagazine.com/forums/read/18.111856-NewClassics-Writing-Theory] for those who want it.) I drew from years of non-professional experience, and the only thing I learned in the process is that writing characters is difficult to do because the term "cliche" is often unearned because the cliches about which people complain are often just any trait a human can be used through which to be relevant to the reader/audience.
Which kind of sucks, if you think about it, but that can't always be helped.
Beyond that, idea osmosis is one of those things I contend with rather constantly. I read a lot of books, which means that if I ever sit down to write something, ideas begin to filter in from just about any source I've ever read from. I can't think of wizards without a little Tolkien [http://en.wikipedia.org/wiki/J._R._R._Tolkien], a little Butcher [http://en.wikipedia.org/wiki/Jim_Butcher], and just a bit Stoker [http://en.wikipedia.org/wiki/Bram_Stoker] and Hamilton [http://en.wikipedia.org/wiki/Laurell_K._Hamilton] when the vampires and such come into play. Children all begin to squeak just a little Rowling [http://en.wikipedia.org/wiki/J.K._Rowling], and nearly any sci-fi elements are either Dietz [http://en.wikipedia.org/wiki/William_C._Dietz] or Adams [http://en.wikipedia.org/wiki/Douglas_Adams] flavored.
The only thing I can complain about is a lot of games tend to pen characters for scenarios, rather than building a character within a game. There is, in my opinion, a good reason for this, but still can be frustrating from the narrative position. Part of a character's depth is how well they fit into the world, and how well the world works with or without the character. Often times, it's hard to get the feel of day-to-day life from the NPCs and the towns as they seem to hold little relevance other than to the protagonist. It makes the entire town, and everyone in it, rather one-dimensional. The problem is that in fleshing out the town and NPCs within, you're writing narrative the player will likely never see or experience. The end result is about twice as much work for very little to no gameplay changes at all. It's a lot of work for a writer, so developers take the intelligent route and don't do it. Not to mention having a narrative going on behind the players' backs can sometimes be alienating. Especially when every character recognizes a city/character/event, but the player doesn't. Or has a group of friends that they get along with, that the player has never met.
I've made plenty of games of the type, and have done the same thing. It's really, really difficult to do that much coding, and it has relatively minimal effects. To point, the game I can think of readily that did this task in full is Shenmue, a game whose budget was $70 million. It's a huge expense, and not one that should be taken lightly, especially since the end result was remarkably minimal in the grand scheme of the game. It was incredibly cool, but still minimal.
As a result, when I see a world that manages to imply goings-on unrelated to the player, and they manage to pull it off well without having to do something huge, I can appreciate it. In particular, Tri-Ace manages to pull it off fairly well for how little is actually done compared to other games in similar genres. The other way to do it is to go big, and code primarily functional AI or daily schedules for games, as seen in Animal Crossing and Shenmue.
But now I'm rambling...
To bring this back on-point, writing characters in general is hard to avoid cliches because a majority of the "stock" characteristics we've seen are that way because they're accurate to human nature and they work. Not to mention that its hard not to do the same thing someone else has done somewhere at some time. There are way too many other games/books/stories/etc. out there for something not to be similar to something else. Inevitably, there's going to be some overlap.
I'm fairly certain I could write unique characters that are mainly different from those we see otherwise in games, but I'm also completely certain that developers should never take me up on that, as that would drive the development time, cost of project, and delayed release dates for very little to no return. And they'd have to pay me to do it.
Honestly, I think it's just fine as it is, and can respect those that do so well given every other limitation out there. I don't think I could do as well as they do given the invisible restraints we don't see as gamers.
