Two of the more critically acclaimed titles for the PlayStation Portable have just joined the Greatest Hits club, making them must own titles for all PSP owners who don't already have the games.

The newly repackaged Greatest Hits games are Ratchet & Clank: Size Matters and Killzone: Liberation. After selling extremely well and being out on shelves for more than a year, Sony decided to repackage the games and drop them to a more attractive price point of USD 19.99 USD.

In Killzone: Liberation, two months after the events of Killzone, most of southern Vekta is still under Helghast control. The rules of war have been cast aside with the Helghast General, Armin Metrac, employing brutal measures in order to seize the initiative and strengthen his position further. Returning as Templar, players will be sent on a covert operation to save hostages captured by Metrac, while ISA troops continue the fight for liberty.

In Ratchet and Clank: Size Matters, the game's main characters are on a much needed vacation but their rest and relaxation time is suddenly cut short as they soon find themselves lured into a mysterious quest. Following the trail of a kidnapped girl, Ratchet and Clank rediscover a forgotten race of genius inventors known as the Technomites. They soon uncover a plot more dangerous than they could have imagined.

These two games mark numbers 31 and 32 of the PSP's Greatest Hits collection, respectively, and are two of the highest quality games that the handheld has to offer.

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