I'm probably also biased but I do believe in the UK (and probably the rest of Europe) it was the Desire. We didn't get the Evo 4G or the Droid so it's hard to compare.
The GS3 has had the biggest global impact by far but I'd say momentum had already turned in favour of Android by the time it was released and it was just a matter of which manufacture could best capitalise on it.
Nexus 4: Stock
HTC Desire: OxygenZM 1.2 rom; Bravo Sense hboot; 4Ext Recovery; S-OFF
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