the GT220 is a very low end-card. not really gaming grade, more for video playback or photo-editing. the 4850 performs admirably in most games. and while its certainly no powerhouse, its more than capable.
^+3 agree with 3 people above...
A GT220 is roughly equal to a 4650 DDR3.
The 4850 is about 4+ tiers above it.
No question. HD 4850 will have the GT220 for breakfast.