Scanned the page, and can only reiterate most of the suggestions...
My first purchase (with the system, even) was Uncharted 2, and I imediately went on Amazon and ordered the original Uncharted once I finished it. (Having to wait a bit before getting the third installment... bloody U.S. economy.)
Metal Gear Solid just released an HD Collection (MGS2, MGS3, and MGS

eace Walker) which I would recommend simply for MGS3, easily my favorite of the series.
inFamous was a rental for me, but if I had the cash, I'd buy inFamous2 in a heartbeat.
Portal2 allows you to download the Steam copy to your computer if you link your PSN accoutn to your Steam account. And, it's a perfect co-op game for date night, if you don't mind getting disassembled* by your significant othera few times.
Heavy Rain was VERY worth the rental. It may seem slow and plod along at times, but for me it was a masterpiece of emotive immersion. So much so that I could only play it without anyone else home, because the storyline upset everyone else so much. Got to "Press 'X' to "Jason!" and was told to 'Turn it off, now.'
*Yay, Johnny5 reference