Most likely you will get more out of it if you compress all 3 games into a single file, instead of 3, because of duplicates.
Example
Code:
GTA3
Streams: 181893 / 181896
Time: 00:08:03 (CPU 00:24:33)
Duplicates: 7305 (54.3 MB) [73.0 MB >> 258 MB]
Size: 4.10 GB >> 8.54 GB >> 8.29 GB
GTA VC
Streams: 370651 / 370652
Time: 00:17:11 (CPU 00:53:26)
Duplicates: 13440 (126 MB) [159 MB >> 522 MB]
Size: 8.83 GB >> 18.2 GB >> 17.7 GB
GTA SA
Streams: 765171 / 765173
Time: 00:34:15 (CPU 01:42:23)
Duplicates: 25733 (198 MB) [270 MB >> 1.06 GB]
Size: 18.4 GB >> 36.6 GB >> 35.5 GB
=
8.29 GB + 17.7 GB + 35.5 GB = 61.5 GB
All together
Streams: 1317713 / 1317719
Time: 00:33:15 (CPU 02:54:31)
Duplicates: 107730 (1.22 GB) [1.66 GB >> 4.26 GB]
Size: 31.3 GB >> 63.4 GB >> 59.1 GB
However this way you will loose the option to install just one of the games.