Which processor is better??

i3 are dual core... so your question doesnt make sense very much. Best performing CPU for gaming taking into account the future would be a quad core i5 2500K. Best gaming performance for the money.

ok,, so more core means better. I am using Intel DC e5400(oc 3.33). will it be able to match quad core at high clock?? will it be able to compete in games equally??

Not all games support 4 core 4 threads. In games that support only 2 cores it will be generally equal to that of a 4 core CPU with same clock speed. In games that support 4 core 4 threads it will not match a quad core CPU at same or even lower clock speed.