BF3 will play on maybe medium-low, Max Payne 3 on probably medium-low, Skyrim on medium, MW3 on medium, Darksiders on medium-low, Crysis 2 on probably low, GTAIV will lag regardless, and the last 2 should work fine.
Hey, BF3 is not a cpu intensive game. He can max it out on 1366x768 res. No problem.
Max payne 3 will run High/medium-high(2x AA)
Skyrim will run on High or more high without lagging.
Not cure about Crysis 2, but he can run more than medium.
He will stuck in GTA4, as it is heavily cpu intensive and gpu as well.
I played those game with my HD6770 @ high setting with 1366x768 res. No lag, but bottleneck. He will less fps than me as 7750 is little bit slower than 6770. But game will not lag on high setting. Only game i stuck is witcher 2 on Ultra setting for my cpu.