The best thing about NBA 2K13 for iOS is the graphics, though there are issues here, too. Courts are crisp and look great, player faces are mostly recognizable, and the animations look great as you're playing. But even on my iPhone 5, which you would assume to be the optimal device for the game, there were significant hiccups and lag while I was playing. It's also important to point out that as of this writing the game does not use the whole iPhone 5 screen, but I'm noticing this is pretty common in the early days of the device while developers catch up.
Game modes in NBA 2K13 are limited to Quick Game, Multiseason, Multiplayer, and Greatest Games. Quick Game lets you pick teams and jump right into a game. Multiseason lets you play through a season then move on to subsequent seasons to try to create a dynasty. Multiplayer lets you match up with other players online or over Bluetooth for single games. These are all fairly standard game modes for a basketball video game.
Greatest Game mode lets you play as current or past superstars like Dirk Novitski, Shaquille O'Neill, or Michael Jordan, trying to match some of their greatest historical games. The only problem is that to match Jordan's 63 points against the Boston Celtics, for example, you would need pinpoint passes, callable plays, and better controls -- things you simply do not have in the iOS version of the game. One more issue I found: in the game, the 63-point game is set in Chicago, when part of what made it so great was that it took place at the Boston Garden. The Jordan fan in me thinks this mistake is unforgivable, but hopefully 2K Sports will catch this error quickly.
Overall, if you don't expect too much, the graphics are good and the gameplay is pretty fun for a quick basketball game with your favorite team. Even though NBA 2K13 is probably the best 5-on-5 basketball on iOS, that is not saying much. Overly simple controls make it difficult to have the authentic experience found on consoles and make this game hard to recommend at the price.