A lot of different games have been released for the iPhone and iPad, but only some of them can boast of really beautiful and modern graphics. Among them there are shooters, strategy games, quests, RPGs, and racing games, completely single and multiplayer (including both MMORPGs and session games).
This list includes all iOS games with good graphics, regardless of their genre and year of release: all of these games have a fairly beautiful appearance for a mobile game.