This is a stealth RCS comparison between the in active service F-22A Raptor, the in production F-35A Lighting II and the prototype PAK FA.
This figures are (obviously) the minimum RCS for the frontal angle.
F-22A Raptor: 0.0001m2
F-35B Lighning II: 0.00143m2
PAK FA: 0.5m2
Some NON-stealth aircraft for comparison:
MiG-31M: 7m2 (unsure of source)
Eurofighter Typhoon FGR4: 0.999m2
Panavia Tornado GR4: 5m2