Far from terrible, but not brilliant either.
This is a game that has very simplistic core gameplay, fly to your objective, destroy bad guys along the way until you finally reach the objective. Then also do battle with the odd end of mission boss battle, most of which are inspired by actual villains from the comic book. Each of these bosses follow a simple pattern and it won't take the average gamer long to work out that pattern and beat the wind out of their opponent.
To defeat each of your opponents you have a nice array of weapons at your disposal, ranging from Iron Man's trademark palm repulsor rays to micro missiles. Each have their preferred use; missiles for heavily armoured targets, gatling gun for regular infantry and repulsors make a good overall weapon that can deal with most situations.
The game's graphics are nothing to be amazed at, but they are not graphics that you can't bear to look at either. However in order to display the mass amounts of carnage that happens on screen most of the time you have to have graphics like this without having some slow down. Which is very nice, especially in this game.
Everytime you complete a mission you can unlock new upgrades for your weapons; make them more powerful, more accurate, increase range etc. the normal biz you'd expect from an action game. The freedom of choice for upgrades here is pretty cool at first, but eventually it all boils down to using a certain weapon so many times in order to unlock the best possible upgrade for it. There are no upgrades that have an advantage over the other so you can't pick out different upgrades for different situation, it just involves you getting the best upgrade possible.
Control wise Iron Man succeeds, to a point. The controls are simple to grasp, flick the wii-mote to melee attack, aim with the wii-mote to shoot, shake the nunchuk to dodge whilst moving in a direction. However though, this happens sometimes even if you move the nunchuk in the slightest, which can become quite an annoyance after a while. One pretty neat addition though, is that if you get killed in action, you get the oppurtunity to 'restart' your heart, by pressing the corresponding buttons at the right time. Though, this only happens more often later in the game, so you may not have quite grasped on how to use it by then. The game is not too long either, you could probably breeze through the game in about ten hours maximum. Then afterwards, if you really want, search out the Stark weapon crates to unlock various artworks from game development.
I would like to recommend this game, however I cannot, since the simple design decisions made by the developers will scare away those who were expecting a much more fleshed out game. Also the game is too short, unless you really like Iron Man I would recommend at least trying it before to see what you think.