I think the N-Gage has sold in less numbers than the AmigaOne!
Seriously the problem is that it was promoted as a games "thing" that did phone "stuff". However its just a normal mobile phone, with a funky layout. No special hardware etc.
However it does set the standard for mobile games developers, so they know what spec they can aim for. Shame about having to remove the battery to change the game. :-o