This is much easier for console titles, played in your living room on a 46" screen. AAA FPS titles offer virtually identical gameplay, but their art assets and thematic direction differentiate them for players.
Selling mobile games based on compelling assets is a touch more difficult. (And that goes double for puzzles)
Absolutely agree. My impression is that Threes tried to do just that with the cute names and faces on tiles as well as the music but it simply isn't in a game like this where the player simply isn't engaged in that way.
Look at Chutes and Ladders. Stunning dumb game mechanic, but the graphics are an asset that makes the game into an asset.
The video game medium doesn't allow one to compete on game mechanics alone.