First, the compression of a piston is not necessarily the the pistons actual compression, but rather the compression ratio that will be yeilded by the cylinder itself when the piston is in your motor. The same piston will yeild different compression ratios depending on the head/block combo.
First, you need to figure out what kind of piston you have: PR3, PR4, P72...ect. As far as oem pistons go, Ls yeild the lowest compression ratio, followed by GSR pistons, then ITR pistons, then b16 pistons, and the higest are ctr pistons.

Here is a rough estimate of the compression ratios that your specific setup will yeild with the different oem pistons.

(information from b20vtec.com)

B16A block, B16 head and:
GS-R pistons 8.7
USDM ITR pistons 9.5
92-93 GS-R pistons 9.56
JDM ITR pistons 9.9
B16A pistons 10.2
CTR pistons 10.8

B16A block, GS-R head and:
GS-R pistons 9.0
USDM ITR pistons 9.9
92-93 GS-R pistons 9.94
JDM ITR pistons 10.3
B16A pistons 10.6
CTR pistons 11.3

B18C block, B16/ITR head and:
GS-R pistons 9.65
USDM ITR pistons 10.6
92-93 GS-R pistons 10.64
JDM ITR pistons 11.0
B16A pistons 11.36
CTR pistons 12.0

B18C block, GS-R head and:
GS-R pistons 10.0
USDM ITR pistons 11.0
92-93 GS-R pistons 11.1
JDM ITR pistons 11.5
B16A pistons 11.9
CTR pistons 12.6

B18B (LS) block, B16/ITR head and:
GS-R pistons 9.8
USDM ITR pistons 10.8
92-93 GS-R pistons 10.84
JDM ITR pistons 11.2
B16A pistons 11.6
CTR pistons 12.3

B18B (LS) block, GS-R head and:
GS-R pistons 10.2
USDM ITR pistons 11.2
92-93 GS-R pistons 11.3
JDM ITR pistons 11.7
B16A pistons 12.1
CTR pistons 12.85