Gradius V (PlayStation 2, 2004)

As a life time fan of the Gradius franchise, I can easily say that this is the hardest entry to the series. Gradius V was developed by the same team that made Ikaruga, the vertical scrolling space shooter for Dreamcast/Gamecube, which in itself was a masterpiece of difficulty. This game has a tendency to fill the screen with enemies and obstacles, all of which can kill you with a single hit. It frequently becomes difficult to keep track of where your ship is, what you're shooting at and what's shooting at you at the same time. This is not a game for people who don't like a challenge.