i dont know how much those sites will pay you in ad revenue, but what i can tell you for certain is that the ios/android i swamped with so much shit that it takes alot to get noticed, and if you do, everybody and their mom is gonna make an app that copies yours. :/ sorta sucks because i would love to develop games for the iphone or android
This is a pretty difficult question to answer, namely because there isn't one.
If developers, from all across the spectrum, were able to tell how much money they'd make from a game then the industry would be a very different place indeed.
A better question would be "can I make a substantial amount of money from a game that I've developed?". To which the answer is "yes, potentially".
For an independent developer, I'd say the smartphone market is your best bet. The upcoming release of console is promising some indie support and you can also develop PC games and release them on Steam but in terms of exposure to a mass market, smartphones are the way.
The money you can make depends on a huge number of factors. For a start, there are multiple sales models you could use. Is the game a one off purchase or is it free? If it's free, is revenue generated through advertising or in-app purchases?
In terms of the game itself, will it be well received? How will it stand out? Has it been done before? How will you market it? Does it integrate with social networking sites to use viral advertising?
One of the biggest factors in all of this is sheer luck. I'm certain that a lot of good games get lost in the ether, whereas simpler games can be hugely successful. Take Doodle Jump, for example. The developers became some of the first app store millionaires for a simple game that involves not much more than some basic accelerometer controls, simple graphics and endless gameplay without plot. I'm sure that their link to an app store approver played some part in their success.
If you don't own a smartphone, I'd say you're at a disadvantage. It means you don't know the market. Whatever platform you decide to go for, make sure you know the market and the trends.
One final thing to consider is the point at which to start making money? For example, your game might make £50. Is that to say it's making money once you've taken off the price of release fees and the cost of the time you've invested?
This all sounds horribly negative; it's not. Developing independent games is a fun an enriching experience and there is always the opportunity to make a lot of money. Whether that opportunity will present itself is a different matter entirely. My advice is make games in your spare time and don't give up your day job.
thanks for all the answers, I'm curious because I reached a level of developing games that could compete with all the crap on those walky talkies. I'm aiming at developing computer games, (dream goal is mmorpgs) nothing close to that yet I'm afraid :)