I have played a lot of games on my PSP but only one game got me really really addicted. For just $9.99, I bought Super Stardust Portable!
Super Stardust Portable for PSP is just like simple flash games like Luminara which requires you to control a ship around a space and blast everything in your path. Sounds kinda simple, but I tell you, it is that simplicity that got me to play it over and over and over again.
The controls are pretty simple. Analog stick to move and the Action buttons to shoot in all 4 (or 8) directions. There are 3 expanding weapons to choose from and the graphics are super nice. Also, it feels kinda like my old game Alien Galaxion X... hehe. Check out the video: