I don't even like plane games, but UN Squadron is AWESOME!
Gameplay: I can say I've never played a flying game that's even close to this one. I love UN Squadron. The only thing in the same ballpark for me is Star Fox, but this is a 2-d side scroller. You get to choose from 3 different pilots right off the bat. One is great at learning weapons quickly (upgrades rapidly), one can use two weapons simultaneously, and the third guy can fly damaged planes. His name is Greg Gates and he's my favorite to use. There's a map-grid with different enemy strongholds to select from. Environments range from submarine battles over the open sea, to desert warfare with gigantic tanks and battle stations. Pick a mission and then prepare for battle. You have a primary machine gun weapon with unlimited ammo, and also a wide variety of special sub-weapons such as torpedos, bombs, napalm, and even a nuke-type weapon. As you play you will earn money to buy better planes. Eventually you will have several different planes and weapons to choose from. Each plane looks and flys differently. Some are good in the sky, some excell at ground attacks, others do it all. Each level contains power-ups and a boss battle at the end. The bosses include battlestations, huge submarines, huge tanks, an aircraft carrier, stealth bombers... you get the idea!
Audio: Well done. Each level has a different sound track which adds to the feel of the environment you're in. The sfx are also solid. Overall the music and sound effects definitely add to the value of this gem.
Pros: You get to choose your favorite pilot and customize each mission. There's lots of different environments and each one is done very well. The bosses are huge, difficult, and extremely fun to blow-up. Wide range of weapons and planes to upgrade. Awesome gameplay and rock-solid graphics and audio.
Cons: Some people may find it too hard, but I like the challenge. Despite it's relative difficulty (even on easy), it's not a really frustrating game.
Gameplay: 10.0
Graphics: 8.5
Audio: 8.0
Difficulty: 8.5
If you're interested - don't rent it, just go out and buy this game! You will not regret it. It would be impossible to NOT like UN Squadron. 9.5!!