Is nvidia geforce 8400GS EXCELLENT FOR PLAYING GAMES LIKE crysis 2

The 8400GS is a very old card, and a step above integrated cards of the day. You might be able to play it at very low resolutions (640X480) with nothing turned on.

Overall, you really should upgrade if you're going to game. If you do need help in upgrading, post your system specs, including the power supply, as well as budget, and we can help find a better card.
 
you can play crysis 2 with this card but at very low resolution and lowest settings....im using a core 2 duo processor with geforce 8400gs and overclocked to 680 mhz with msi afterburner and played fifa12 and crysis2 with minimal settings.seriously speaking this is not a gaming card,you need to get a new card for playing games like crysis2,fifa12 etc at max setting...lower resolution and lower setting will allow u to play crysis2 but your gameplay experience will not be that good........
 

That's the whole point of "backwards compatibility", it should support whatever card you choose and if it doesn't then kick up a fuss with the cards manufacturer.