There are a series of recently released reports on invention available here: http://web.mit.edu/invent/report.html
Invention (coming up with new ideas) is the precursor to innovation (the process of commercialising new ideas). Sometimes the two get lumped together in thinking terms and I think it would be useful to consider issues involved with them separatly, especially for the emerging indy scene in australia.
The innovation side of finding the commercial or non-commercial business model(s) to get the product out there is a different ball game altogther.
Putting the two together in a viable business model is also a challenge.
Anyways, I think the reports are well worth reading if you want some general insight and focused anlaysis on this important area.
After all, all games start with an itch scratching the back of somebody's mind.
I was told that you can have a new idea, but someone else will have always thought of it. It's getting that idea published and released, first, that counts. And even then, generally someone will have always tried. The most originality we get out of it, these days, is how we present it, and the natural diferentiating found in the diversity of human perspectives - a natural thing since we're all born and raised in different environments and situations, etc.
I'm not sure if I believe what I was told is true in all areas, but I thought I'd mention it anyway.
I wouldn't want to devalue anyone out there that is bright/creative and has a tonne of ideas floating around in their head...but I totally agree with Angel in that, most of the time, the ideas have been had and/or executed previously and there are probably other people working on the same thing at the moment.
Now in regards to the game mechanics...
The most important skill a wannabe/established designer can have if they want to differentiate themselves is to be able to present those ideas to the audience better than the previous designer and to constantly push the boundaries and limitations of that idea.
For example, the 'FPS' concept was at one stage, just an idea floating around in someone's head...but since that has been made mainstream, what we can experience and achieve within a FPS style of gameplay has been pushed further than what it was originally expected to. Not many people will tell you that Catacombs Abyss is as good as Half Life etc etc. Not many people actually know of, or have played Catacombs Abyss either.
My point is, if you look at Half Life objectively, it does nothing different to Doom (or even your average 2D platformer).
Using those foundations (as 'uncreative' as it is perceived to be) and building on top them is what we pretty much have to do, whether we do it consciously, or unconsciously.
I guess what does bother me though, is that people forget the fundamentals. The foundations of the FPS are not 'you shoot people from the point of view of the character'...the foundation upon which FPS is built is the concept of experiencing a conflict through the character's eyes.
Which is why we see so few 'Deus Ex's, 'Theif's etc and more 'Far Cry's (yes I'm still working on that big ass text about objective gameplay). To me, game mechanics aren't so much about innovation as they are about gradual evolution of a concept.
As for game technology...
I think the development of more fluid interfacing devices is always going to be susceptible to the concept of invention/innovation. The eye-toy being the all-to-common example. Things like graphics technology and development also fall under this category. The S3 Virge (?) was an example of invention/innovation and took an old concept and made it commercially viable. This is part of the 'interface' between the computer and the player (as much as we don't think of it like that anymore). Anything regarding 'output' goes into my design methodology as 'interface' and requires design of its own, and hence anything such as graphics, sound etc is driven by innovation.
I know no-one's bothered looking at this for ages, but...
New ideas are old ideas dressed up in a different way. That doesn't stop them being new ideas. However, it's really a "glass half-full, glass half-empty" problem. Ideas are only as good as how clearly they are expressed (or implemented in the case of games).
Ideas have no intrinsic value, culturally or financially, unless you can express or implement it. I've learnt this the hard way, having been an "ideas person" for way too long, never understanding that until I had designed it, drawn it and/or coded it, I had achieved nothing.
And the ironic thing is, the longer you talk about it, the more time it's going to take to get it done! :) So on that note, I shall end.