It's not easy making a good Kinect game. Just look at Steel Battalion, which tried to leverage the Kinect in a unique way, and ended up getting eviscerated by critics and gamers alike. It takes more than hands-free motion controls to make a satisfying Kinect game. A lot more.
So what does it take to make a good Kinect game? Based on experience, it's a game that mixes simple, easy-to-perform gestures with some kind of multiplayer component. Marvel Avengers: Battle for Earth appears to nail both sides of the equation, and mixes in some solid cel-shading aside. If it's looking for a niche with kids seeking to act out the roles of their favorite heroes, then it's probably going to fill it pretty nicely.
The basics are pretty simple. Every character--from Iron Man to Hulk to Spider-Man--has a set number of gestures. Raise your arms up, and Spider-Man will jump into the air. Swing your arms down, and he will swing in for an attack. There are kicks, and punches, and even a golf club-like swing from Hulk that will knock a foe into the air for a couple dozen punches.
Such physical actions are what help to separate the various heroes from one another. Iron Man shoots beams (thrust arms out), Spider-Man swings (jump and kick), and Hulk does what a Hulk does: smash. Of them all, Hulk is the most enjoyable to use, mainly because his physical combat style meshes perfectly with the Kinect. It's one thing to feel force feedback from a controller when performing a Hulk action. It's quite another to be smashing stuff yourself. It's odd that a Kinect game should feel as ... kinetic ... as Marvel Avengers, but it somehow manages to pull it off.
Of course, it doesn't go much deeper than that. The actual strategy, well, it's overall pretty minimal. Every battle is a tag team match, so a lot of the strategy is down to knowing when to switch out (just look at your character's health bar). It's also possible to interrupt enemy attacks; and if your meter is high enough, launch a devastating super attack. Overall, it's quite easy to build up momentum with a series of smaller strikes, then crush an opponent with a devastating super attack.
But strategy isn't really the point, is it? The point of most Kinect games is to get up, get a little exercise, and laugh as you punch Hulk into the next solar system. In that, Marvel Avengers already has the potential to be more successful than Steel Battalion, which made the mistake of introducing too much nuance into the motions (putting the self-destruct right next to the smoke vent, for instance). All of Marvel's moves are simple to understand, easy to pull off, and available right there on the screen.
For some, this type of praise might feel a little backhanded. Oh yes, the Kinect is only good for silly party games and brawlers, you might say. Well, no. The Kinect just happens to have a very specific, very narrow niche right now. That niche is to effectively 'put you in the game.' Try and go too far or too deep with the mechanics, and you risk ending up with a Steel Battalion.
Marvel Avengers is the sort of physical, easy-to-understand fighter that is perfect for young kids who are in the process of discovering how cool Wolverine really is (answer: really cool). In that, the most likely audience for Marvel Avengers is for parents and young kids who are looking to continue basking in the glow cast by The Avengers earlier this summer. It would be a little much to suggest that Marvel Avengers: Battle for Earth captures the essence of being a superhero. But it sure is fun to play.