Ratchet and Clank is good times, definitely recommended.
As for you kern, are you asking about MGS? I think you are, so to answer your question I would say it would definitely help you get the most out of Portable Ops if you played all the previous games. You can probably play it and understand it for the most part, but you would miss out on a lot of the in-jokes and nuances.
You really can't go wrong with trying to find some used copies of 2 and 3. They are really some of the best gaming experiences I've ever had.
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