Good idea, bad presentation.
The idea of this game is good, because it's the basic humans vs aliens scenario, but the game itself is not very good at all. The entire idea of the game isn't using strategy, it's seeing whoever has upgraded their stuff more and can spam faster. You earn money entirely too fast in land battles. One round I actually ended up with 94,000 coins, while still spamming all my buttons. Air and Water battles are beyond boring, because there are only 4 different unit types, some of which being about as useful as throwing a can at the enemy's base. Then there are even some land units that are useless as well, such as the most expensive infantry on the alien side, the power blast. They're slow, weak, and their range is matched easily by any of the units on the human side. This game is a decent one, but honestly, there are MANY other games on the portal that do what this one does much better.
In summary though, here are the things you should improve upon.
1. Make the units more balanced. When the most expensive infantry on one side is dying to the cheapest and fastest infantry on the opposite side, even with full life and damage skills, something is terribly wrong.
2. Make the game less about unit spamming, and more about using the right units to counter the enemy's units. Going along with this is also a slower acquisition of coins, to prevent said unit spamming.
3. Instead of the enemy losing health when your units get off the screen, make them lose health by having the units actually ATTACK the enemy base. It makes no sense that simply running past the base results in it being blown up.
4. Take away the melee units. It's the equivalent of bringing a knife to a gun fight honestly. Trying to use a sword alien against a ranged human just doesn't work unless something else randomly flings itself in the way to take the first bullet.
5. Add base defenses such as turrets to the game that you can place on the 3 rows. All it takes is 1 hole in your defenses and you lose unless you've shelled out upgrade points on base defenses, and even then, once a hole is punched, you're very unlikely to get that defense back.
6. Make the armored units such as tanks more durable. A sword alien I sent out killed a tank in one hit. ONE HIT. This brings back to the balance issue.
I appreciate your submission, and I can definitely see that a lot of work was put into this, but you need to refine the idea before it truly becomes a great game.