Are you just starting off? if you have some programming experience you could just try making a 2d walk simulator with flash or unity after that just build on it. imho its the atmosphere that makes a great impression, but its the gameplay and/or story that must keep it interesting. I recommend something simple and not serious first, to get a grasp on how it works.
Is there any restriction on how you have to make the game? If not, engines like Construct, or RPG Maker VX Ace can make some really impressive games with great ease, AND they have free Lite versions. They're both fantastic places to start if you're a beginner at development.
