Some statistics
20 Games:
91 Gb in ISO
54.7Gb on Uncompressed WIA (WBFS should be about same size) without update partition (compression of 40%)
33.6Gb on 7z compressed WIA without update partition (compression of 38.57% respect to WIA, 63% to ISO)
Those are some wonderful 60Gb to fill with more games.
edit: updated with 10 more games, overall compression in respect to ISO doesn't change barely 62% of saved space, which is a lot.
previous 20 games plus new 10 Games (30 games in total):
ISO 145.3Gb
WIA 86.4Gb compression of 40.5%
7Z 55.2Gb compression of 36% respect to WIA, 62% to ISO
edit2:
and with 14 more games (44 in total)
ISO 207Gb
WIA 114.8 compression of 44.5%
7Z 75.2Gb compression of 34.5% respect to WIA, 63.7% to ISO
edit3:
and with 5 more games (49 in total)
ISO 228.8Gb
WIA 118.3 compression of 48.3%
7Z 77.5Gb compression of 34.5% respect to WIA, 66% to ISO