To date, this is as good as mobile graphics get.
Shadowgun's greatest strengths are its control scheme and striking good looks. The developers managed to nail button-less cover, a brave design decision when creating a game where cover is as important as in other similar shooters such as Gears of War. Simply by approaching cover, the on-screen character will slide into place and be firmly cemented until the player pulls straight back on the floating virtual stick.
I never experienced any real pains or frustrations with the scheme. If I had to nitpick about anything, it would be that not all objects you find will be objects your character can use to take cover. However, before you make it half way through the first of the eight levels, you'll have a good understanding of what constitutes potential cover and what doesn't.
Shadowgun looks so good on the iPhone's screen that you may find yourself stopping to take in the scenery on more than one occasion. The lack of jagged edges would be enough to make even the high-end PC gamer jealous, lest they be equipped with the latest in graphical hardware. Textures appear detailed, edges are round and smooth, and the effects, while a bit unorthodox, are enough to make you feel the intensity of the battle.
For all its beauty, one of Shadowgun's greatest failing is in the utter lack of variety. It's a shame that the graphical fidelity isn't highlighted further by the addition of more outdoor scenarios, a larger cast of enemy combatants, or more than one basic location. I'm sad to report that I began feeling a sense of deja vu through a few sections, as if I'd already been there and fought through this corridor before. Every time I thought we were going to have a real change of scenery, the game pulls you back to a place all too familiar.
The other problem, while not as critical as the former, is the story. Not only is it disjointed, but it borrows heavily from other games (something that becomes quite clear after defeating the final boss). While the concept of borrowing heavily from some of the more successful console and PC titles isn't new, it's still a little disappointing. Mobile gaming is a new frontier, so developers should be doing what they can to treat it as such.
Without a doubt Shadowgun's strengths greatly outweigh its weaknesses. The controls are tight and appropriate, it looks simply fantastic, and what it lacks in variety it makes up for in gameplay and excellent pacing. Even though the negatives may appear to some to be deal breakers, it is without question that the game is truly a good time. That's what is most important.