Depending on how much and how you use your phone, battery life can vary greatly. You just cannot compare keeping your screen on with phone in Airplane Mode and without touching it to taking pictures with GPS and data on.
Check out this
discussion for more arguments.
And if you wanna compare different devices' screen on time, please give EXACT details about your usage patterns.
Nokia 5110 > Alcatel OT303 > Nokia 3310 > Nokia 1100 > Nokia 1112 > Nokia 5000 > Nokia 6555 > Nokia 3120C > Nokia E51 > Nokia E52 > Motorola Defy > Galaxy Nexus > Nexus 5
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