In Earth Defence Force 2017, you blow up thousands of giant bugs, mechs, and space ships. Need I say more?
You start off with a limited range of weapons, but you end up unlocking many more throughout the campaign. The missions can be a little repetitive, but you can't complain that blowing up aliens is no fun. As the story progresses, you encounter bigger and bigger baddies and you continue to blow them up with rocket launchers, machine guns, sniper rifles, and countless other weapons.
It may not be the deepest game, but Earth Defence Force is fun as hell to play!