I too have long legs by proportion.

Height : 175 cm
Inseam length : 85 cm

My ratio of inseam length to height is almost 1 : 2. I do think that longer legs will help in cycling. Compare two different people with everything the same except for the length of the legs, wouldn't the person with the longer leg produce more power? Since there will be more muscle fibres, more power should be produce. Please correct me if I'm wrong. Quote me! HEHE

While legs are only one part of cycling, they are important! Please note they are not everything though.