The PSP is kinda notorious now for not really having too many great games .To be quite frank, I would have to agree since I know I would've sold my PSP a while back had it not been for one series of games. That series is the DJ Max series
The DJ max series of games are basically Beatmania clones with a couple of tweaks. Notes scroll down in with the music and you must hit the right button at the appropriate time. What separates DJ Max from Beatmania is the fact that you can change the scrolling speed at anytime to make some notes much easier to hit. Also, in DJ Max you can you can switch the appearance of some of the notes and even the HUD, which they call the gear for some reason. The DJ Max series had its start on PC and is now branching out to PSP and Arcade. The first entry to the PSP is DJ Max portable.
The song list in this game offers a good variety of genres and songs to choose from, albeit with a bias towards more dance songs , it is a rhythm game after all. Depending on your skill level, the game offers different note charts that require fewer/more buttons. These note charts are 4 buttons, 6 buttons, and 8 buttons; you do however have to unlock 8 button mode (though if you are new to the series it'll be a while before you are able to stand your own with 8 buttons).
Speaking of unlockables, there are a TON of unlockables in DJ Max portable. . Unlockables range from hidden songs, gears, notes, and some extra stuff like movies and images that you can't even use in the game itself. This is really great for people who want replayability and like to unlock stuff (I know I do). The two ways you unlock stuff is by playing songs and getting a certain amount of combos. While playing a certain amount of songs is somewhat standard for these kind of games, unlocking stuff by combos is more tedious than it should be. The reason for this is because you can only unlock one thing via combo per play through; the sheer amount of unlockables makes this the longest and most annoying stuff to get.
Another problem with this game is that the note charts don't seem to accommodate the fact that you are using the PSP. Since you are basically limited to your thumbs, and in some cases your index fingers, you can't really pull of some of the stuff that you can on PC. DJ Max portable also really isn't very friendly to new players because of this. Depending on which version of this game you get, the original or international version, you may also not get the option to change the menus to English. In the games defense though there isn't many menus in the original version that will trip up the non-Korean speaker.
Although a little rough around the edges, the first DJ Max for the PSP is still a good game for DJ Max veterans. For everyone else though, there are better DJ Max game on the PSP at this point and is only really worth checking out after you've had ample time with the series.