If you look up games for the iPhone on youtube for example, you can find tons of sweet games that have on screen buttons since the iPhone has no programmable hardware keys or d-pad.
Checkout this link to see what I mean
http://www.youtube.com/watch?v=cdxwvkv3fRg check 1m30s!
Isn't any company making games such as this with on screen buttons / d-pad to combat the ever increasing issue of phones without physical keyboards, multiple hardware keys and d-pads?? Most physical d-pads are only 6-way not 8 and can't do diagonal anyways. An on screen d-pad could do everything.
Also, I have yet to find a site where you can search for games that have on screen buttons, or a site that accurately filters games for a phone such as the Imagio that are FULLY working (ie: pocketgear, handango)