I once saw Angry Birds for Mac got much less download and ratings than AB for iOS, then feeling there are 2 different kinds of users on 2 different platforms.
Such casual games for iOS/smart phones can easily play on PC/Mac as flash games, very popular, free and easy to find; however when convert to smartphones game, the control/design should change a lot or it will fail and vice versa for smart phone games converted back to PC/Mac games. The strength of PC/Mac is 4 arrow keys which are very useful for most PC/Mac games, but putting those keys on smartphones, it covers 1/4 of the screen and very difficult to control.
For shooting (battle tank or FPS) games or strategy games or fighting game is easy to control by 101 keyboard & mouse; however when porting to smartphone become ridiculous hard to play, with 2 of my thumbs cover half of the screen, my enjoyment reduced by half.
Porting game around multiple platforms may be good under developer view, but because your game is not designed for specific platform, it's easy to fail.