Make "Clones" of Video Games
If you have never made a finished game before making a clone is an excellent idea. Making a clone can be fun, adding different features to a "boring" clone and make it into something new and exciting can be very satisfying. One user from TIGsource talks about spicing up their clone:
The first full game my friends an I made is basically a match 3 game... but we wanted to make it fun for us to play. So we added physics, and have tons of balls falling on top of each other, and lightning bolts and exploding balls, stuff we thought was cool.
Clones are also nice as a starter project because you will most likely have lots of reference material that you can look at. Many tutorials and informational materials are available on how to make a Defender clone or Galaga clone, or perhaps the most common, the Pong Clone.
Sure it is not as romantic and exciting as making the next best FPS/dating simulator, but it is nice to work on something and actually know where you are going with it from the get-go. Make a video game clone to see the beginning of what's really involved with making a game from scratch.
One thing you should not plan for is making money, especially on a clone. We also suggest you clone something other than Tetris since the Tetris Holdings LCC's only purpose these days is to hunt and shut down clones. There will be an overwhelming urge to copy what others did as a pathway to success, but just because it worked once doesn't mean it will work again. Remember, games are more than just the mechanics behind them, but every part working as a whole.
Watch, read, listen to the video game postmortems and understand some of the grievances the original developers had. Use this to inform the game design beyond its original intent, and take it as a design challenge to implement what the original designers had envisioned.