I disagree. Yes there are a lot of Sudoku apps out there but most of them are ugly. I bought the only one that I think has a decent design. And I would probably buy one that came out with really nice graphics and nice ux.
Yes, those pretty graphics are important, and people getting their first sodoku game on the phone may switch to your game because of them. But almost everybody that likes sodoku already has one installed, and they still have to find you at their search results.
How many new Android phones are activated every day?