Eclipse is one of the most popular board games around right now -- it's a vast, involving epic "4X" game, where those four Xs stand for eXploration, eXpansion, eXploitation (as in mining crops and resources from various planets), and eXtermination (as in finishing off your alien opponents). It was recently announced that Big Daddy's Creations would be adapting the game for iPad, and the iOS version has now arrived on the App Store, available for $6.99.
As a board game, I think Eclipse is terrific -- it's very well balanced, and all of the various things you can do offer plenty of different strategies to play with. There are three resources (money, science, and material) that you can use to exert your influence on various areas of a galaxy, research new technologies for starships or your empire, or build up those ships and other various structures to combat your enemies. The game's almost endlessly flexible, in that you can try to win over the game's nine turns in any number of ways.
The drawback here, however, is that all of that flexibility and complexity make the game, well, complicated. This is not a casual game by any means, and while the iOS version's interface is fairly good at converting all of the information you need into a visible, touchable form, it's not very good at actually explaining what all of that information is. So when you're confronted by 30-50 icons on screen at the same time and asked to choose one, the game can be overwhelming to say the least.
Still, if you like great board games and are up for a challenge, Eclipse is excellent. And if you're already familiar with the board game, then this might end up becoming one of your favorite games on the App Store. My only other complaint is that there's no real "metagame" to it -- winning or losing the various games you play doesn't matter much in the larger picture at all. Still, Eclipse is an incredible adaptation of a brilliant board game, and it comes highly recommended. Even at the price of $6.99, it's one of the best board game apps out there.