Conventional wisdom would hold that the -500 has the best range since it's the shrink. But no.
From our very own http://www.airliners.net/info
Max cruising speed 908km/h (491kt), long range cruising speed 794km/h (429kt). Range with 128 passengers and standard fuel 3362km (1815nm), range with 128 pax and max fuel 4973km (2685nm). High gross weight version max range 6300km (3400nm) with 140 passengers.
Max cruising speed 912km/h (492kt), long range cruising speed 813km/h (439kt). Standard version range with max payload 4005km (2160nm), typical range with 146 passengers 3630km (1960nm). High gross weight option range with 146 passengers 3850km (2080nm).
Max cruising speed 912km/h (492kt), economical cruising speed 795km/h (430kt). Standard range with max passengers 2815km (1520nm), higher gross weight option range with max passengers 4444km (2400nm).
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo